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The impact of the physical environment and phytoplankton size on particle types (zooplankton, biogenic matter or phytodetritus) in the water column is poorly understood. Here, we investigate how hydrography (e.g. water column stratification) impacts phytoplankton size and photophysiology across a productive coastal bank area. Additionally, we investigate how the physical environment and phytoplankton size structure influence the concentrations of plankton (e.g. copepods and diatom chains), biogenic forms (fecal pellets) and other particles (minerals, aggregates or phytodetritus) using discrete samples and in-situ optical instruments. Microphytoplankton (>20 µm), including many chain-forming diatoms, dominated (average > 90% of total size fraction) in un-stratified waters of the bank. Phytoplankton within the bank region also required more irradiance to saturate photosynthesis, as indicated by the onset light saturation parameter (Ek, average 297 µmol photons m−2 s−1), suggesting high plasticity to a dynamic light environment. Conversely, the contribution of nano- and picophytoplankton ( 1 × 103 counts m−3), fecal pellets (>1 × 104 counts m−3) and ammonium (>0.5 µM) within the bank compared to off-bank regions, indicated that copepods were actively grazing in this region. Low stratification (average stratification index (SI) 5 × 105 counts m−3) within the bank when compared to off-bank (SI off-bank > 10 × 10−3 kg m−4). Our results, obtained using automated techniques measured in-situ, represent an innovative approach to demonstrate that phytoplankton size and stratification influence the nature of particles found in the water column (including aggregates, fecal pellets and grazer abundances).

Plankton are an extremely diverse and polyphyletic group, exhibiting a large range in morphological and physiological traits. Here, we apply automated optical techniques, provided by the pulse‐shape recording automated flow cytometer—CytoSense—to investigate trait variability of phytoplankton and plastidic ciliates in Arctic and Atlantic waters of the subpolar North Atlantic. We used the bio‐optical descriptors derived from the CytoSense (light scattering [forward and sideward] and fluorescence [red, yellow/green and orange from chlorophyll a , degraded pigments, and phycobiliproteins, respectively]) and translated them into functional traits to demonstrate ecological trait variability along an environmental gradient. Cell size was the master trait varying in this study, with large photosynthetic microplankton (> 20 μ m in cell diameter), including diatoms as single cells and chains, as well as plastidic ciliates found in Arctic waters, while small‐sized phytoplankton groups, such as the picoeukaryotes (μ m) and the cyanobacteria Synechococcus were dominant in Atlantic waters. Morphological traits, such as chain/colony formation and structural complexity (i.e., cellular processes, setae, and internal vacuoles), appear to favor buoyancy in highly illuminated and stratified Arctic waters. In Atlantic waters, small cell size and spherical cell shape, in addition to photo‐physiological traits, such as high internal pigmentation, offer chromatic adaptation for survival in the low nutrient and dynamic mixing waters of the Atlantic Ocean. The use of automated techniques that quantify ecological traits holds exciting new opportunities to unravel linkages between the structure and function of plankton communities and marine ecosystems.

Microalgae have unique adaptions including low metabolic activity, utilization of lipid storage, and resting stage formation to survive the Polar Night. Some species are mixotrophic or heterotrophic and do survive periods that are not favorable for photosynthetic (autotrophic) growth, such as the Polar Night. In addi- tion, the autotrophic and mixotrophic species seem to maintain the key components of the photosynthetic apparatus intact during the dark period, which allows them to resume growth rapidly once light comes back in spring. In contrast, some macroal- gal species may act as “season anticipators” and utilize the winter darkness or early spring period as their major growth seasons. This chapter elucidates aspects of the ecology of micro- and macroalgae with a focus on the dark season. It is comprised of six parts and starts with an introduction (Sect. “Introduction”) about Arctic marine micro- and macroalgae. Section “The Key Abiotic Environmental Variables Related to Micro- and Macroalgae” reviews the key abiotic environmental variables related to micro- and macroalgal growth and survival. The seasonal development of the different groups of microalgae is described in Sect. “Microalgae”, comprising phytoplankton, microphytobenthos, and sea-ice algae. Section “Macroalgae” intro- duces the three classes of macroalgae (phaeo-, rhodo-, and chlorophytes) with infor- mation about biological variables, seasonal processes, and habitats. Section “Ecophysiology of Algae in the Polar Night” sheds light on the ecophysiology of microalgae and macroalgae in the Polar Night, using selected examples. The last Section “Conclusive Remarks” summarizes our current state of knowledge and provides some conclusions derived from it.

The phytoplankton in coastal regions are responding to constant environmental changes, thus the use of proxies derived from in situ frequent time-series observations and validated from traditional microscopic or pigment methods can be a solution for detecting rapid responses of community dynamics and succession. In this study, we combined in situ high-frequency (every 30 min from May to September 2017) optical and hydrographic data from a moored buoy and weekly discrete samplings to track phytoplankton community dynamics and succession in Mausund Bank, a highly productive region of the coast of Norway. Three hydrographic regimes were observed: mixing period (MP) in spring, onset of stratification (transient period, TP) in summer and a stratified period (SP) in fall, with occasional strong winds that disrupted the surface stratification in the beginning of September. A bloom dominated by the diatom Skeletonema costatum was observed in the MP due to intense mixing and nutrient availability, while flagellates prevailed in nutrient-poor waters during the TP, followed by a bloom dominated by rhizosolenid diatoms (Proboscia alata and Guinardia delicatula), when stratification peaked. A mixed assemblage of diatoms (e.g. Pseudo-nitzschia), coccolithophores and dinoflagellates occurred during the SP, as strong winds reintroduced nutrients to surface waters. Through pigment (chemotaxonomy) and microscopic observations, we tested, for the first time in a coastal region, whether an ‘optical community index’ derived from in situ measurements of chlorophyll a fluorescence (Fchla) and optical particulate backscattering (bbp) is suitable to differentiate between diatom versus flagellate dominance. We found a negative relationship between Fchla:bbp and diatom:flagellate, contrary to previous observations, possibly because of the influence of non-algal contribution (e.g. zooplankton, fecal pellets and detritus) to the bbp pool in highly productive systems. This finding suggests that such relationship is not universal and that other parameters are needed to refine the optical community index in coastal regions. 0278-4343/© 2020 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/)

Trace metal or rare earth element (REE) content of marine macroalgae are underexamined and there is a great need for further understanding since macroalgae are used for food and may also be bioindicators of environmental changes. This study, by using high resolution inductive coupled plasma spectrometer in a clean laboratory (class 1000), investigates the trace metal and REE concentrations and composition in the youngest tissue of various species within three algal classes in the Trondheimsfjord, Norway, comprising phaeo-, chloro-, and rhodophytes in winter (February) and Spring (May) 2013, with the main focus on phaeophytes. The macroalgae were found in a clear zonation pattern as a function of depth. A significant difference in element concentration and composition was found between the six phaeophyte species along with a significant difference between winter and spring tissue. A zonation depth trend in algal tissue element concentration was also found for the phaeophytes, where the algal species located in both extreme ends (upper vs. lower littoral zone) obtained a lower element concentration than the algae located in the middle part of the littoral zone. This trend seems to result from different algal contact with the metal-rich sea surface microlayer. The chlorophytes had 5-27 times higher concentration of REE and lead (Pb) than the two other algal classes. Results indicate that the rhodo- and chlorophytes are better accumulators than the phaeophytes for several trace metals and REE.

The importance of newly formed sea ice in spring is likely to increase with formation of leads in a more dynamic Arctic icescape. We followed the ice algal species succession in young ice (≤ 0.27 m) in spring at high temporal resolution (sampling every second day for 1 month in May–June 2015) in the Arctic Ocean north of Svalbard. We document the early development of the ice algal community based on species abundance and chemotaxonomic marker pigments, and relate the young-ice algal community to the communities in the under-ice water column and the surrounding older ice. The seeding source seemed to vary between algal groups. Dinoflagellates were concluded to originate from the water column and diatoms from the surrounding older ice, which emphasizes the importance of older ice as a seeding source over deep oceanic regions and in early spring when algal abundance in the water column is low. In total, 120 taxa (80 identified to species or genus level) were recorded in the young ice. The protist community developed over the study period from a ciliate, flagellate, and dinoflagellate dominated community to one dominated by pennate diatoms. Environmental variables such as light were not a strong driver for the community composition, based on statistical analysis and comparison to the surrounding thicker ice with low light transmission. The photoprotective carotenoids to Chl a ratio increased over time to levels found in other high-light habitats, which shows that the algae were able to acclimate to the light levels of the thin ice. The development into a pennate diatom-dominated community, similar to the older ice, suggests that successional patterns tend toward ice-associated algae fairly independent of environmental conditions like light availability, season or ice type, and that biological traits, including morphological and physiological specialization to the sea ice habitat, play an important role in colonization of the sea ice environment. However, recruitment of ice-associated algae could be negatively affected by the ongoing loss of older ice, which acts as a seeding repository. Copyright © 2018 Kauko, Olsen, Duarte, Peeken, Granskog, Johnsen, Fernández-Méndez, Pavlov, Mundy and Assmy. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

Here it is reported the first detection of DV-chl a together with the usual chl a in the marine dinoflagellate Alexandrium ostenfeldii from the Baltic Sea. Growth response and photosynthetic parameters were examined at two irradiances (80 and 240 μmol photons m(-2) s(-1)) and temperatures (15 °C and 19 °C) in a divinylic strain (AOTV-OS20) versus a monovinylic one (AOTV-OS16), using in vivo chl a fluorescence kinetics of PSII to characterize photosynthetic parameters by pulse amplitude modulated fluorescence, (14)C assimilation rates and toxin analyses. The divinylic isolate exhibited slower growth and stronger sensitivity to high irradiance than normal chl a strain. DV-chl a : chl a ratios decreased along time (from 11.3 to < 0.5 after 10 months) and to restore them sub-cloning and selection of strains with highest DV-chl a content was required. A mutation and/or epigenetic changes in the expression of divinyl reductase gene/s in A. ostenfeldii may explain this altered pigment composition. Despite quite severe limitations (reduced fitness and gradual loss of DV-chl a content), the DV-chl a-containing line in A. ostenfeldii could provide a model organism in photosynthetic studies related with chl biosynthesis and evolution.

Biofouling on cultivated kelp in open sea conditions is a challenge when fouling species such as the encrusting bryozoans Membranipora membranacea and Electra pilosa develop colonies that cover the surface of the kelp lamina. The bryozoan colonies make the flexible lamina brittle and susceptible to breakage and reduce the commercial value of the biomass for both human consumption and industrial applications. The development of the bryozoan fouling on cultivated Saccharina latissima in temperate coastal waters was studied at two locations in Norway from April to September. The time of settling and development of colonies of M. membranacea and E. pilosa were characterized. Sampling of bryozoan larvae abundance at the cultivation locations showed that the bryozoan colonies settled on the cultivated kelp in mid-June at both locations, followed by a rapid colony growth during late June and July. In August and September, the kelp was highly degraded by the bryozoan coverage and highly subjected to breakage of the lamina. Membranipora membranacea was the most prevailing of the two species. Although abundant at all cultivation depths, the results showed a decrease in bryozoan coverage with increasing depth. From a commercial point of view, S. latissima deployed in temperate Norwegian coastal waters in winter should be harvested in early June to avoid the negative impact from bryozoan fouling.

Diatoms are a keystone algal group, with diverse cell morphology and a global distribution. The biogeography of morphological, functional, and life-history traits of marine diatoms were investigated in Arctic and Atlantic waters of the Labrador Sea during the spring bloom (2013-2014). In this study, trait-based analysis using community-weighted means showed that low temperatures (< 0°C) in Arctic waters correlated positively with diatom species that have traits such as low temperature optimum growth and the ability to produced ice-binding proteins, highlighting their sea ice origin. High silicate concentrations in Arctic waters, as well as sea ice cover and shallow bathymetry, favoured diatom species that were heavily silicified, colonial and capable of producing resting spores, suggesting that these are important traits for this community. In Atlantic waters, diatom species with large surface area to volume ratios were dominant in deep mixed layers, whilst low silicate to nitrate ratios correlated positively with weakly silicified species. Sharp cell projections, such as processes or spines, were positively correlated with water-column stratification, indicating that these traits promote positive buoyancy for diatom cells. Our trait-based analysis directly links cell morphology and physiology with diatom species distribution, allowing new insights on how this method can potentially be applied to explain ecophysiology and shifting biogeographical distributions in a warming climate. Copyright © 2018 Fragoso, Poulton, Yashayaev, Head, Johnsen and Purdie. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

Source at https://doi.org/10.1007/s00300-018-2278-5. Under-ice blooms of phytoplankton in the Chukchi Sea have been observed, with strong implications for our understanding of the production regimes in the Arctic Ocean. Using a combination of satellite remote sensing of phytoplankton biomass, in situ observations under sea ice from an autonomous underwater vehicle (AUV), and in vivo photophysiology, we examined the composition, magnitude and origin of a bloom detected beneath the sea ice Northwest of Svalbard (Southern Yermak Plateau) in May 2010. In situ concentration of up to 20 mg chlorophyll a [Chl a] m−3, were dominated by the northern planktonic spring species of diatoms, Thalassiosira nordenskioeldii, T. antarctica var. borealis, Chaetoceros socialis species complex and Fragilariopsis oceanica. These species were also found south of the marginal ice zone (MIZ). Cells in the water column under the sea ice were typically high-light acclimated, with a mean light saturation index (Ek) of 138 μmol photons m−2 s−1 and a ratio between photoprotective carotenoids (PPC) and Chl a (w:w) of 0.2. Remotely sensed data of [Chl a] showed a 32,000 km2 bloom developing south of the MIZ. In effect, our data suggest that the observed under-ice bloom was in fact a bloom developed in open waters south of the ice edge, and that a combination of northward-flowing water masses and southward drifting sea ice effectively positioned the bloom under the sea ice. This have implications for our general understanding of under-ice blooms, suggesting that their origin and connection with open water may be different in different regions of the Arctic.

This is a post-peer-review, pre-copyedit version of an article published in Polar Biology. The final authenticated version is available online at https://doi.org/10.1007/s00300-018-2368-4. The jellyfish Periphylla periphylla, which can have strong ecological impacts on its environment, is ubiquitous in the Norwegian Sea and its range was predicted to extend northwards. The occurrence of P. periphylla in the northern Barents Sea increased since 2014 and, for the first time, several individuals were collected within a high Arctic fjord (> 78°N) in western Spitsbergen in January 2017. The low solar irradiance prevailing during the polar night and an increased inflow of relatively warm Atlantic water in the European Arctic since the last decade likely provide suitable conditions for the medusa to colonize Svalbard’s fjords during the winter months. However, light avoidance constrains the photophobic P. periphylla to deeper offshore areas during the midnight sun period. The current occurrence of P. periphylla in high Arctic fjords during the polar night will have a limited impact on marine ecosystems in the short term, but long-term effects are more uncertain if its abundance continues to increase.

Source at: https://doi.org/10.1675/063.040.0301 Visually-oriented predators, such as seabirds, are highly light dependent, and thus their presence and activity under continuously dark conditions of Arctic polar night pose a number of questions about the strategies and mechanisms they use to find prey. Here, opportunistic observations of the behaviors of Thick-billed Murres (Uria lomvia; n = 4) and juvenile Black Guillemots (Cepphus grylle; n = 5) were made in the ocean around Spitsbergen Island, Svalbard Archipelago, off the coast of Norway. These observations were made between 15-23 January 2014-2017 during the darkest period of the polar night. Underwater observations recorded on 23 January 2014 and 19-20 January 2015 revealed that individual birds seemed to be attracted to artificial light. They actively foraged in the sea within the beam of scuba diver lights and harbor lamps indicating that artificial light may create additional feeding opportunities for seabirds present in the area. Other observations of Dovekies (Alle alle; n = 2) made on 15-16 January 2016 may indicate that not all seabird species exhibit such an adaptable behavior. Various seabird reactions might be caused also by different age and intra-specific variation among individuals; however, due to the limited number of observations, future studies are needed to increase our understanding of these behaviors.

Diel vertical migration (DVM) of zooplankton is a global phenomenon, characteristic of both marine and limnic environments. At high latitudes, patterns of DVM have been documented, but rather little knowledge exists regarding which species perform this ecologically important behaviour. Also, in the Arctic, the vertically migrating components of the zooplankton community are usually regarded as a single sound scattering layer (SSL) performing synchronized patterns of migration directly controlled by ambient light. Here, we present evidence for hitherto unknown complexity of Arctic marine systems, where zooplankton form multiple aggregations through the water column seen via acoustics as distinct SSLs. We show that while the initiation of DVM during the autumnal equinox is light mediated, the vertical positioning of the migrants during day is linked more to the thermal characteristics of water masses than to irradiance. During night, phytoplankton biomass is shown to be the most important factor determining the vertical positioning of all migrating taxa. Further, we develop a novel way of representing acoustic data in the form of a Sound Image (SI) that enables a direct comparison of the relative importance of each potential scatterer based upon the theoretical contribution of their backscatter. Based on our comparison of locations with contrasting hydrography, we conclude that a continued warming of the Arctic is likely to result in more complex ecotones across the Arctic marine system.

Reflection spectra obtained from hyperspectral imaging can be used as a bio-optical taxonomic identification tool if the pigment composition and the corresponding optical absorption signatures of an organism are known. In this study we elucidate species-specific absorption and corresponding reflection signatures of marine organisms and discuss optical fingerprints from underwater hyperspectral imaging (UHI) for future automated identification of organisms on the seafloor. When mounted on underwater robots, UHI has the potential to be a time- and cost-efficient identification and mapping method covering large areas over a short time. Hyperspectral imaging in vivo and in situ were used to obtain species-specific reflection signatures (optical fingerprints). High performance liquid chromatography, liquid chromatography–mass spectroscopy and nuclear magnetic resonance were used for pigment identification and to obtain species-specific absorption signatures of four marine benthic species; the spoonworm Bonellia viridis, and the sponges Isodictya palmata, Hymedesmia paupertas and Hymedesima sp. Species-specific optical fingerprints based on a UHI-based reflectance signature were verified successfully in the organisms investigated.

Recent studies have shown that the biological activity during the Arctic polar night is higher than previously thought. Zooplankton perform diel vertical migration during the dark period/winter, with the calanoid copepods Calanus spp. being one of the main taxa assumed to contribute to the observed diel vertical migration. We investigated the sensitivity of field-collected Calanus spp. to irradiance by keeping individuals in an aquarium and exposing them to gradually increasing irradiance in white, blue, green, and red wavebands, recording their phototactic response with a near-infrared-sensitive video camera. Experiments were performed with the two oldest copepodite stages as well as adult males and females. The copepods were negatively phototactic, and the lowest irradiance eliciting a significant phototactic response was of the order of 10−8–10−6 μmol photons m−2 s−1 for white, green, and blue wavebands, whereas the comparative irradiance for red wavebands was up to three orders of magnitudes higher. The different copepod developmental stages displayed different sensitivities to irradiance. During the darkest part of the polar night, the lowest irradiance for significant response corresponded to 0.0005–0.5 % of the ambient surface irradiance, depending on light source. Accordingly, Calanus spp. may respond to irradiance from the night sky down to 70–80 m, moonlight to 120–170 m, and aurora borealis down to 80–120 m depth. The high sensitivity to blue and green light may explain the Calanus’ ability to perform diel vertical migration during the polar night when intensity and diurnal variation of ambient irradiance is low.

This study examines the composition and activity of the planktonic community during the polar night in the high Arctic Kongsfjord, Svalbard. Our results are the first published evidence of bioluminescence among zooplankton during the Arctic polar night. The observations were collected by a bathyphotometer detecting bioluminescence, integrated into an autonomous underwater vehicle, to determine the concentration and intensity of bioluminescent flashes as a function of time of day and depth. To further understand community dynamics and composition, plankton nets were used to collect organisms passing through the bathyphotometer along with traditional vertical net tows. Additionally, using a moored bathyphotometer closed to the sampling site, the bioluminescence potential itself was shown not to have a diurnal or circadian rhythm. Rather, our results provide evidence for a diel vertical migration of bioluminescent zooplankton that does not correspond to any externally detectable changes in illumination.

As for many deep-sea animals, the red colouration of the two amphipods Eurythenes gryllus and Anonyx sp. has an important function providing camouflage, as the attenuation of the red wavelengths in seawater is higher than other colours within the visible range. Variation in colouration between different stages of colour intensity (related to size) is evident in both species. The red colour is caused by carotenoids, and the carotenoid composition was identified and quantified using spectral optical density signatures, high-performance liquid chromatography (HPLC) and liquid chromatography–mass spectrometry (LC–MS). The carotenoid astaxanthin was identified as the major carotenoid in both amphipods, both in pure and in esterified forms. In addition, minor amounts of lutein-like, canthaxanthin-like and several unidentified carotenoids were found in E. gryllus, while diatoxanthin, β,β-carotene and canthaxanthin-like carotenoids were detected in Anonyx sp. Generally, both species displayed an increase in the amount of carotenoids as a function of colour intensity and size. Shifts in λmax in the OD (Optical density; dimensionless, acronym absorbance) spectra were evident in both species between the different colour stages in both the in vivo and the in vitro material, probably caused by changes in pigment composition. Similar shifts in λmax were observed between the in vivo and in vitro pigment raw extracts in general, most likely caused by pigment-binding proteins. The differences in pigment composition and wavelength shifts suggest large intra- and inter-specific differences between the two species. Probable reasons for changes in pigment composition could be related to diet, season, moulting patterns, metabolic pathways and reproduction.

The photosynthetic functionality in chloroplasts in the two sacoglossan molluscs Placida dendritica and Elysia viridis from the Trondheim fjord in Norway was studied. P. dendritica and E. viridis with no functional chloroplasts in their digestive system were introduced to the green macroalgae Codium fragile. Our results showed that P. dendritica was not able to retain functional (photosynthetic) chloroplasts. Transmission electron microscopy (TEM) showed that chloroplasts were directly digested when phagocytosed into the digestive cells. Four stages of chloroplast degradation were observed. A corresponding operational quantum yield of chl a fluorescence (ΦPSII ~ 0) indicated autofluorescence, and the presence of highly degraded chl a supported these observations. In contrast, E. viridis was able to retain functional chloroplasts. For this species it took only 1 week for the chloroplasts inside the digestive cells to acquire the same ΦPSII and light utilisation coefficient (α) as C. fragile kept under the same light conditions. Data for 8 days showed a 2–6-fold increase in the maximum photosynthetic rate (Pmax) and light saturation index (Ek) relative to C. fragile. This increase in available light was probably caused by a reduced package effect in the digestive gland of E. viridis relative to C. fragile, resulting in a partial photoacclimation response by reducing the turnover time of electrons (τ). Isolated pigments from C. fragile compared to E. viridis showed the same levels of photosynthetic pigments (chl a and b, neoxanthin, violaxanthin, siphonaxanthin, siphonein and β,e-carotene) relative to μg chl a (w:w), indicating that the chloroplasts in E. viridis did not synthesise any new pigments. After 73 days of starvation, it was estimated that chloroplasts in E. viridis were able to stay photosynthetic 5–9 months relative to the size of the slugs, corresponding to an RFC of level 8 (a retention ability to retain functional chloroplasts (RFC) for more than 3 months). The reduction in ΦPSII, Pmax and α as a function of time was caused by a reduction in chloroplast health and number (chloroplast thylakoid membranes and PSII are degraded). These observations therefore conclude that chloroplasts from C. fragile cannot divide or synthesise new pigments when retained by E. viridis, but are able to partially photoacclimate by decreasing τ as a response to more light. This study also points to the importance of siphonaxanthin and siphonein as chemotaxonomic markers for the identification of algal sources of functional chloroplasts.

High-latitude environments show extreme seasonal variation in physical and biological variables. The classic paradigm of Arctic marine ecosystems holds that most biological processes slow down or cease during the polar night. One key process that is generally assumed to cease during winter is diel vertical migration (DVM) of zooplankton. DVM constitutes the largest synchronized movement of biomass on the planet, and is of paramount importance for marine ecosystem function and carbon cycling. Here we present acoustic data that demonstrate a synchronized DVM behaviour of zooplankton that continues throughout the Arctic winter, in both open and ice-covered waters. We argue that even during the polar night, DVM is regulated by diel variations in solar and lunar illumination, which are at intensities far below the threshold of human perception. We also demonstrate that winter DVM is stronger in open waters compared with ice-covered waters. This suggests that the biologically mediated vertical flux of carbon will increase if there is a continued retreat of the Arctic winter sea ice cover. The article has been published as open access under CC-BY version 4.0.

The aim of my thesis is to elucidate the different pathways of light in the marine environment, from underwater irradiance to the absorption of photons in microalgae. The pathway is followed through light harvesting and the subsequent electron transfer, to the fuelling of the photosynthetic process (Fig. 1.1, Papers 1, 2 & 3). In addition, the effect of temperature on photosynthesis and respiration in pelagic and benthic microalgae has been investigated (Papers 3 & 4). A novel approach to estimate the light absorption in Photosystem II (PSII) is evaluated in combination with Pulse Amplitude Modulated (PAM) fluorescence measurements, to calculate the rate of photosynthetic oxygen production (Paper 2). The approach was evaluated against measured rates of oxygen production and 14C-assimilation, as a function of temperature (Papers 2 & 3).

PSII-fluorescence kinetics, and 14 C-incorporation rates in monocultures of the marine phytoplankton species Prorocentrum minimum (Pavill.) J. Schiller (Dinophyceae), Prymnesium parvum f. patelliferum (J. C. Green, D. J. Hibberd et Pienaar) A. Larsen (Coccolithophyceae), and Phaeodactylum tricornutum Bohlin (Bacillariophyceae), grown at 15� C and 80 lmol photons AEm )2 AEs )1 . Photosynthesis versus irradiance curves were measured at seven temperatures (0� C‐30� C) by all three approaches. The maximum photosynthetic rate (P C max) was strongly stimulated by temperature, reached an optimum for Pro. minimum only (20� C‐25� C), and showed a similar relative temperature response for the three applied methods, with Q10 ranging from 1.7 to 3.5. The maximum light utilization coefficient (a C ) was insensitive or decreased slightly with increasing temperature. Absolute rates of O2 production were calculated from pulse-amplitude-modulated (PAM) fluorometry measurements in combination with biooptical determination of absorbed quanta in PSII. The relationship between PAM-based O2 production and measured O2 production and 14 C assimilation showed a species-specific correlation, with 1.2‐3.3 times higher absolute values of P C max and a C when calculated from PAM data for Pry. parvum and Ph. tricornutum but equivalent for Pro. minimum. The offset seemed to be temperature insensitive and could be explained by a lower quantum yield for O2 production than the theoretical maximum (due to Mehler-type reactions). Conclusively, the PAM technique can be used to study temperature responses of photosynthesis in microalgae when paying attention to the absorption properties in PSII. Key index words: 14 C assimilation; microalgae; O2

The marine environment represents a largely untapped source for isolation of new microorganisms with potential to produce biologically active secondary metabolites. Among such microorganisms, Gram-positive actinomycete bacteria are of special interest, since they are known to produce chemically diverse compounds with a wide range of biological activities. We have set out to isolate and characterize actinomycete bacteria from the sediments in one of the largest Norwegian fjords, the Trondheim fjord, with respect to diversity and antibiotic-producing potential. Approximately 3,200 actinomycete bacteria were isolated using four different agar media from the sediment samples collected at different locations and depths (4.5 to 450 m). Grouping of the isolates first according to the morphology followed by characterization of isolates chosen as group representatives by molecular taxonomy revealed that Micromonospora was the dominating actinomycete genus isolated from the sediments. The deep water sediments contained a higher relative amount of Micromonospora compared to the shallow water samples. Nine percent of the isolates clearly required sea water for normal growth, suggesting that these strains represent obligate marine organisms. Extensive screening of the extracts from all collected isolates for antibacterial and antifungal activities revealed strong antibiotic-producing potential among them. The latter implies that actinomycetes from marine sediments in Norwegian fjords can be potential sources for the discovery of novel anti-infective agents.

Bioluminescence commonly influences pelagic trophic interactions at mesopelagic depths. Here we characterize a vertical gradient in structure of a generally low species diversity bioluminescent community at shallower epipelagic depths during the polar night period in a high Arctic fjord with in situ bathyphotometric sampling. Bioluminescence potential of the community increased with depth to a peak at 80 m. Community composition changed over this range, with an ecotone at 20–40 m where a dinoflagellate-dominated community transitioned to dominance by the copepod Metridia longa. Coincident at this depth was bioluminescence exceeding atmospheric light in the ambient pelagic photon budget, which we term the bioluminescence compensation depth. Collectively, we show a winter bioluminescent community in the high Arctic with vertical structure linked to attenuation of atmospheric light, which has the potential to influence pelagic ecology during the light-limited polar night. © The Author(s) 2016. This work is licensed under a Creative Commons Attribution 4.0 International License. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in the credit line; if the material is not included under the Creative Commons license, users will need to obtain permission from the license holder to reproduce the material. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/

In spring 2005, monthly sampling was carried out at a sublittoral site near Tautra Island. Microphytobenthic identification, abundance (ABU), and biomass (BIOM), were performed by microscopic analyses. Bacillariophyceae accounted for 67% of the total ABU, and phytoflagellates constituted 30%. The diatom floristic list consisted of 38 genera and 94 species. Intact light-harvesting pigments chl a, chl c, and fucoxanthin and their derivatives were identified and quantified by HPLC. Photoprotective carotenoids were also observed (only as diadinoxanthin; no diatoxanthin was detected). Average fucoxanthin content was 4.57 ± 0.45 μg fucoxanthin · g sediment dry mass⁻¹, while the mean chl a concentration was 2.48 ± 0.15 μg · g⁻¹ dry mass. Both the high fucoxanthin:chl a ratio (considering nondegraded forms) and low amounts of photoprotective carotenoids indicated that the benthic microalgal community was adapted to low light. Microphytobenthic primary production was estimated in situ (MPPs, from 0.15 to 1.28 mg C · m⁻² · h⁻¹) and in the laboratory (MPPp, from 6.79 to 34.70 mg C · m⁻² · h⁻¹ under light saturation) as ¹⁴C assimilation; in April it was additionally estimated from O₂-microelectrode studies (MPPO₂) along with the community respiration. MPPO₂ and the community respiration equaled 22.9 ± 7.0 and 7.4 ± 1.8 mg C · m⁻² · h⁻¹, respectively. A doubling of BIOM from April to June in parallel with a decreasing photosynthetic activity per unit chl a led us to suggest that the microphytobenthic community was sustained by heterotrophic metabolism during this period.

We studied the variability of in vivo absorption coefficients and PSII-scaled fluorescence excitation (fl-ex) spectra of high light (HL) and low light (LL) acclimated cultures of 33 phytoplankton species that belonged to 13 different pigment groups (PGs) and 10 different phytoplankton classes. By scaling fl-ex spectra to the corresponding absorption spectra by matching them in the 540–650 nm range, we obtained estimates for the fraction of total chl a that resided in PSII, the absorption of light by PSII, PSI, and photoprotective carotenoids. The in vivo red peak absorption maxima ranged from 673 to 679 nm, reflecting bonding of chl a to different pigment proteins. A simple approach is presented for quantifying intracellular self-shading and evaluating the impact of photoacclimation on biooptical characteristics of the different PGs examined. In view of these results, parameters used in the calculation of oxygenic photosynthesis based on pulse-amplitude-modulated (PAM) and fast-repetition-rate (FRR) fluorometers are discussed, showing that the ratio between light available to PSII and total absorption, essential for the calculation of the oxygen release rate (using the PSII-scaled fluorescence spectrum as a proxy) was dependent on species and photoacclimation state. Three subgroups of chromophytes exhibited 70%–80%, 60%–80%, and 50%–60% chl a in PSII-LHCII; the two subgroups of chlorophytes, 70% or 80%; and cyanobacteria, only 12%. In contrast, the mean fraction for chromo- and chlorophytes of quanta absorbed by PSII was 73% in LL- and 55% in HL-acclimated cells; thus, the corresponding ratios 0.55 and 0.73 might be used as correction factors adjusting for quanta absorbed by PSII for PAM and FRR measurements.

Since 1998, a heterokont flagellate initially namedChattonella aff. verruculosa has formed recurrentextensive blooms in the North Sea and the Skager-rak, causing fish mortalities. Cells were isolatedfrom the 2001 bloom off the south coast of Norway,and monoalgal cultures were established and com-pared with the Chattonella verruculosa Y. Hara etChihara reference strain NIES 670 from Japan. Thecells in Norwegian cultured isolates were very vari-able in size and form, being large oblong (up to34 lm long) to small rounded (5–9 lm in diameter)with two unequal flagella, numerous chloroplasts,and mucocysts. The SSU and partial LSU rDNAsequences of strains from Norway and Japan werecompared and differed by 0.4% (SSU) and 1.3%(LSU), respectively. Five strains from Norway wereidentical in the LSU rDNA region. Phylogeneticanalyses based on heterokont SSU and concatenatedSSU + LSU rDNA sequences placed C. aff. verrucul-osa and the Japanese C. verruculosa within the cladeof Dictyochophyceae, with the picoflagellate Florenci-ella parvula Eikrem as the closest relative. Ultrastruc-ture, morphology, and pigment compositionsupported this affinity. We propose the nameVerrucophora farcimen sp. et gen. nov. for this flagellateand systematically place it within the class Dictyoch-ophyceae. Our studies also show that C. verruculosafrom Japan is genetically and morphologically dif-ferent but closely related to V. farcimen. The speciesis transferred from the class Raphidophyceae to theclass Dictyochophyceae and renamed Verrucophoraverruculosa. We propose a new order, Florenciellales,to accommodate V. farcimen, V. verruculosa, andF. parvula.Key index words: carotenoids; Chattonella; Dictyo-chophyceae;harmfulalgae;LSUrDNA;newtaxon;phylogeny; SSU rDNA; ultrastructureAbbreviations: G,gamma;GTR,general timereversible; I, proportion of invariable sites;MCMC, Markov chainMonteCarlo; ML, maximumlikelihoodIn April–May 1998, a heterokont phytoflagellateformed a massive bloom in the North Sea and theSkagerrak, off the coasts of Germany, Denmark,Sweden, and Norway, which killed 350 tons offarmed salmon as well as some feral fish (Aure et al.2001, Backe-Hansen et al. 2001). The responsibleorganism was initially identified as Chattonella aff.verruculosa because it resembled this speciesdescribed from Japan, but differed somewhat in cellsize, form, and growth pattern compared to previ-ous studies (Hara et al. 1994, Yamaguchi et al.1997). A bloom of a similar organism took place inApril–May 2000 in the German Bight and off theDanish Jutland coast (Lu and Go¨bel 2000). In 2001,C. aff. verruculosa again caused fish mortalities inNorway, and 1100 tons of reared salmon were killed.This time, the massive bloom developed in coldwaters (about 2 C–5 C) in the Kattegat and the

The epifauna associated with two of the most common species of kelp in the Arctic, Laminaria digitata (Hudson) Lamouroux, 1813 and Saccharina latissima (Linnaeus) Lane, , Mayes, Druehl and Saunders 2006 [synonym: L. saccharina (Linnaeus) Lamouroux, 1813] were examined in Kongsfjorden, Svalbard. The aim of this study was to test whether species richness of epifauna was influenced by seasonality of recruitment supply (spring and summer) or by age of the substrate (lamina). From 20 algae specimens (ten—L. digitata, ten—S. latissima), a total of 27 epifaunal taxa were identified with bryozoans as the most species-rich group. Total species richness ranged from one to nine species per lamina. No significant difference in species richness was observed between the two kelp species. In both macroalgae, more epifauna taxa were registered on lamina in May (mean 6) than in August (mean 3). This indicates that the time chosen for sampling had a significant impact on the species richness pattern. The number of epifaunal species was significantly negatively correlated with increasing age of the lamina. There are indications that diversity of the epifauna on lamina is influenced to a large extent by substrate (lamina) surface area, environmental stress and the presence of meroplankton in the water column.

The potential impact of drill cuttings on the two deep water calcareous red algae Mesophyllum engelhartii and Lithothamnion sp. from the Peregrino oil field was assessed. Dispersion modelling of drill cuttings was performed for a two year period using measured oceanographic and discharge data with 24 h resolution. The model was also used to assess the impact on the two algae species using four species specific impact categories: No, minor, medium and severe impact. The corresponding intervals for photosynthetic efficiency (ΦPSIImax) and sediment coverage were obtained from exposure-response relationship for photosynthetic efficiency as function of sediment coverage for the two algae species. The temporal resolution enabled more accurate model predictions as short-term changes in discharges and environmental conditions could be detected. The assessment shows that there is a patchy risk for severe impact on the calcareous algae stretching across the transitional zone and into the calcareous algae bed at Peregrino.

The interaction between the marine phototrophic dinoflagellate Prorocentrum minimum and associated bacteria was studied in different physico-chemical environments in batch cultures. In stagnant cultures the dinoflagellates aggregated at the surface, while with low shear induced by gentle stirring and turbulent mixing induced by bubbling, the cells were dispersed. Both pH and O2 concentration eventually increased in the stagnant and stirred cultures as a result of photosynthesis. Bacterial community dynamics, productivity and composition was monitored by direct cell counts, plate counts, 3H-leucine incorporation, richness of genomes estimated by PCR-DGGE and frequency of growth rate types on agar plates. Bacterial productivity and diversity was restrained in both stagnant and stirred cultures, compared with bubbled ones. This pattern was observed early, before bulk water was affected by metabolic activity, which suggests that algal aggregation was not a prerequisite for inhibition of bacterial growth. Increased bacterial production during stationary growth phase of the algae in stagnant and stirred cultures suggests that high pH or O2 concentration were not the most important inhibiting factors. Rather, the need for turbulent mixing suggests that the structure of the extracellular organic material must be modified to make it available to bacteria. One growth rate type in the bacterial community was not inhibited in stagnant and stirred cultures and developed similarly in all cultures.

Chl a and C-normalized pigment ratios were studied in two dinophytes (Prorocentrum minimum and Karlodinium micrum), three haptophytes (Chrysochromulina leadbeateri, Prymnesium parvum cf. patelliferum, Phaeocystis globosa), two prasinophytes (Pseudoscourfieldia marina, Bathycoccus prasinos) and the raphidophyte Heterosigma akashiwo, in low (LL, 35 μmol photons m−2 s−1) and high light (HL, 500 μmol photons m−2 s−1). Pigment ratios in LL and HL were compared against a general rule of photoacclimation: LL versus HL ratios ≥1 are typical for light-harvesting pigments (LHP) and 1 with some exceptions such as Chl c3 in P. globosa and MV Chl c3 in C. leadbeateri. LL/HL to Chl a ratios of photosynthetic carotenoids were close to 1, except Hex-fuco in P. globosa (four-fold higher Chl a ratio in HL vs LL). Although pigment ratios in P. globosa clearly responded to the light conditions the diadinoxanthin-diatoxanthin cycle remained almost unaltered at HL. Total averaged pigment and LHP to C ratios were significantly higher in LL versus HL, reflecting the photoacclimation status of the studied species. By contrast, the same Chl a-normalized ratios were weakly affected by the light intensity due to co-variation with Chl a. Based on our data, we suggest that the interpretation of PPC and LHP are highly dependent on biomass normalization (Chl a vs. C).

Changes in pigmentation, bio-optical characteristics and photophysiology, during phytoflagellate succession in mesocosms

Chemical composition of the microalga Thalassiosira pseudonana Hasle & Heimdalwas studied with different proton nuclearmagnetic resonance (1H NMR)techniques, and by comparing NMR spectrafrom extraction samples with a spectrumfrom a sample of whole cells we show thathigh-resolution magic angle spinning (HRMAS) 1H NMR can be used for broadrange analysis of metabolic composition inmicroalgal whole cells. Signals fromimportant metabolites such aspolyunsaturated fatty acids (PUFAs)eicosapentaenoic (EPA) and docosahexaenoic(DHA) acids were seen in a 1H NMRspectrum of lipophilic extract, andpossibly also signals from the carotenoidfucoxanthin. In a spectrum of hydrophilicextract we assigned signals to amino acidssuch as glutamine (Gln) and glutamic acid(Glu), carbohydrate and ATP. These findingswere compared to a spectrum of HR MAS1H NMR analysis of whole cells, whereit was possible to find signals coincidentwith the different metabolites seen inspectra of the extraction samples. Sincethe position of resonance peaks in a NMRspectrum depends on the chemicalsurroundings of each atom at the time ofanalysis some peak shift differencesbetween extract and whole cell samplespectra may occur, but signal shifts werenot significantly different between theanalyses here. In addition, application ofHR MAS highly increased spectral resolutionin the complex whole cell sample. Wetherefore suggest that HR MAS 1H NMRanalysis is a suitable analysis tool tostudy metabolic composition directly onwhole cells of microalgae, making itpossible to study a broad range ofmetabolites simultaneously without tediousextraction procedures.

Published version. Source at http://doi.org/10.1016/j.pocean.2015.08.005. Several recent lines of evidence indicate that the polar night is key to understanding Arctic marine ecosystems. First, the polar night is not a period void of biological activity even though primary production is close to zero, but is rather characterized by a number of processes and interactions yet to be fully understood, including unanticipated high levels of feeding and reproduction in a wide range of taxa and habitats. Second, as more knowledge emerges, it is evident that a coupled physical and biological perspective of the ecosystem will redefine seasonality beyond the ‘‘calendar perspective”. Third, it appears that many organisms may exhibit endogenous rhythms that trigger fitness-maximizing activities in the absence of light-based cues. Indeed a common adaptation appears to be the ability to utilize the dark season for reproduction. This and other processes are most likely adaptations to current environmental conditions and community and trophic structures of the ecosystem, and may have implications for how Arctic ecosystems can change under continued climatic warming.

The utility of absorbance and fluorescence-emission spectra for discriminating among microalgal phylogenetic groups, selected species, and phycobilin- and non-phycobilin-containing algae was examined using laboratory cultures. A similarity index algorithm, in conjunction with fourth-derivative transformation of absorbance spectra, provided discrimination among the chlorophyll [Chl] a/phycobilin (cyanobacteria), Chl a/Chl c/phycobilin (cryptophytes), Chl a/Chl b (chlorophytes, euglenophytes, prasinophytes), Chl a/Chl c/fucoxanthin (diatoms, chrysophytes, raphidophytes) and Chl a/Chl c/peridinin (dinoflagellates) spectral classes, and often between/among closely related phylogenetic groups within a class. Spectra for phylogenetic groups within the Chl a/Chl c/fucoxanthin, Chl a/Chl c/peridinin, Chl a/phycobilins and Chl a/Chl c/phycobilin classes were most distinguishable from spectra for groups within the Chl a/Chl b spectral class. Chrysophytes/diatoms/raphidophytes and dinoflagellates (groups within the comparable spectral classes, Chl a/Chl c/fucoxanthin and Chl a/Chl c/peridinin, respectively) displayed the greatest similarity between/among groups. Spectra for phylogenetic groups within the Chl a/Chl c classes displayed limited similarity with spectra for groups within the Chl/phycobilin classes. Among the cyanobacteria and chlorophytes surveyed, absorbance spectra of species possessing dissimilar cell morphologies were discriminated, with the greatest range of differentiation occurring among cyanobacteria. Among the cyanobacteria, spectra for selected problematic species were easily discriminated from spectra from each other and from other cyanobacteria. Fluorescence-emission spectra were distinct among spectral classes and the similarity comparisons involving fourth-derivative transformation of spectra discriminated the increasing contribution of distinct cyanobacterial species and between phycobilin- and non-phycobilin-containing species within a hypothetical mixed assemblage. These results were used to elucidate the application for in situ moored instrumentation incorporating such approaches in water quality monitoring programmes, particularly those targeting problematic cyanobacterial blooms.

Coralline algae constitute a cosmopolitan group of calcifying rhodophytes (red algae) that display characteristic optical fingerprints due to light absorption by specific light-harvesting pigments. The spectrally conspicuous nature of coralline algae makes them potential candidates for optical remote sensing surveys. Recently, underwater hyperspectral imaging (UHI), which we believe is a novel optical remote sensing technique, also has become the subject of marine research. The aim of the study was to characterize the spectral properties of different coralline algal species and to assess the potential of UHI as a coralline algal identification and mapping tool. Four species of coralline algae were investigated: Corallina officinalis, Lithothamnion glaciale, Phymatolithon lenormandii, and Phymatolithon tenue. Important coralline algal pigments were identified using spectrophotometry and high-performance liquid chromatography (HPLC). Reflectance spectra of all species were obtained using both a spectrometer and UHI. Multivariate statistical analyses were performed on the reflectance data to identify spectral differences between the species and the instruments. Supervised classification of coralline algae in UHI transects recorded both in vivo and in situwas also carried out. 𝑅�R-phycoerythrin and chlorophyll a were found to be the most dominant coralline algal pigments. The analyzed species of coralline algae displayed highly similar reflectance spectra, and dips in reflectance corresponding to the absorbance peaks of 𝑅�R-phycoerythrin and chlorophyll a were identified in all spectra. Wavelengths corresponding to 𝑅�R-phycoerythrin light absorbance were the greatest contributors to interspecific spectral differences, but the investigated coralline algal species could not be spectrally distinguished with great accuracy. Optical signatures recorded using different instruments were comparable, but inter-instrumental spectral differences were found to be greater than interspecific differences. Supervised UHI classification was unable to accurately map different coralline algal species due to the similarity of the optical fingerprints; however, as a group, coralline algae could easily be identified. In the future, large-scale UHI surveys of coralline algal habitats should be carried out using platforms such as remotely operated vehicles (ROVs) and autonomous underwater vehicles (AUVs) to enhance our understanding of this widespread and ecologically important organism group. © 2017 Optical Society of America. One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modifications of the content of this paper are prohibited.

Literature data on diversity of photosynthetic activity in Opisthobranchia are reviewed and new histological data presented on the presence of zooxanthellae in members of the nudibranch clade Cladobranchia. Zooxanthellae are recorded here for the first time in members of the family Arminidae (Dermatobranchus) and in the aeolid Piseinotecus gabinierei. Although a broad histological survey on Nudibranchia has been performed, only species of the taxon Cladobranchia are reported to house zooxanthellae. A new method to measure photosynthesis is applied to opisthobranchs with chloroplasts and zooxanthellae. With a Pulse Amplitude Modulated Fluorometer (PAM), the chlorophyll a fluorescence and corresponding fluorescence yield (electron transfer) of photosynthetically active chloroplasts or zooxanthellae can be analyzed in vivo. This facilitates better understanding of the diversity of zooxanthella and chloroplast uptake (ranging from feeding up to highly evolved forms of symbiosis) in the different opisthobranch clades.

The effects of alarm substance on feeding behaviour of zebra danio fish (Brachydanio rerio) were tested by offering them high and low densities of enclosed waterfleas (Daphnia magna). Normally the fish attacked high densities of prey, but when exposed to alarm substance they preferred lower and presumably less confusing prey densities — also lowering their feeding rate.

A toxic phytoplankton bloom, dominated by the prymnesiophyte Chrysochromulina leadbeateri Estep, developed in the Ofotfjord–Tysfjord area (North Norway) in mid-May and ended in late June 1991 in Vestfjorden and the adjacent fjord areas. Chrysochromulina leadbeateri dominated at total cell densities of >2 × 106 cells·L−1; at lower total cell densities, C. leadbeateri was accompanied by other Chrysochromulina species, peridinin-containing dinoflagellates, and diatoms. Bio-optical characteristics and pigmentation in laboratory and field strains of C. leadbeateri allowed for the interpretation of the optical signatures within the bloom. The bio-optical data suggested healthy and actively growing cells during the bloom. About 600 metric tons of pen-raised Atlantic salmon were killed by the C. leadbeateri bloom. A laboratory study was conducted to assess the potential impact of finfish on C. leadbeateri growth. It was found that the polyamine putrescine enhanced cell biomass and hemolytic activity. Given this, a possible scenario for the development of this bloom and the level of toxicity is hypothesized: (1) The nutrient loading in the Ofotfjord area was enhanced during the winter of 1990–1991 due to the overwintering of 1.5 × 106 metric tons of herring from a depth of 0–250 m. This may have sustained a large stock of the mixotrophic C. leadbeateri in early spring before light regime (irradiance, spectral irradiance, and day length) made net photosynthesis possible. (2) The release of polyamines during the decay of dead fish (e.g. putrescine, cadaverine, and histamine) may have acted as cofactors with ichthyotoxins making “hypertoxic complexes” with the polyamines enhancing growth in the mixotrophic C. leadbeateri.

Due to the selective attenuation of solar light and the absorption properties of seawater and seawater constituents, free-floating photosynthetic organisms have to cope with rapid and unpredictable changes in both intensity and spectral quality. We have studied the transcriptional, metabolic and photo-physiological responses to light of different spectral quality in the marine diatom Phaeodactylum tricornutum through time-series studies of cultures exposed to equal doses of photosynthetically usable radiation of blue, green and red light. The experiments showed that short-term differences in gene expression and profiles are mainly light quality-dependent. Transcription of photosynthesis-associated nuclear genes was activated mainly through a light quality-independent mechanism likely to rely on chloroplast-to-nucleus signaling. In contrast, genes encoding proteins important for photoprotection and PSII repair were highly dependent on a blue light receptor-mediated signal. Changes in energy transfer efficiency by light-harvesting pigments were spectrally dependent; furthermore, a declining trend in photosynthetic efficiency was observed in red light. The combined results suggest that diatoms possess a light quality-dependent ability to activate photoprotection and efficient repair of photodamaged PSII. In spite of approximately equal numbers of PSII-absorbed quanta in blue, green and red light, the spectral quality of light is important for diatom responses to ambient light conditions. © 2014 Valle et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

The impact on downwelling irradiance of phytoplankton, cromophoric dissolved organic matter (CDOM) and particulate inorganic carbon (PIC) in the form of coccoliths, is described using a radiative transfer model and field data from the Barents Sea (BS). While annual Emiliania huxleyi blooms in the BS have been detected with satellite remote sensing, this is the first bio-optical field study on E. huxleyi from this area. Bio-optical variables were measured in August 2007 along a transect through the Polar Front from Arctic Water (ArW) into an E. huxleyi bloom in Atlantic Water (AW). The depth of the euphotic zone was on average 52m in ArW, 45m in frontal mixed water (FMW) and 21m in AW. At the 10% irradiance depth in AW, phytoplankton had attenuated 40%, CDOM 17% and PIC 18% of the irradiance from 400 to 700nm. Numbers from ArW were 36%, 26% and pot) in AW was 1.8× higher than in ArW, and PIC had reduced PP pot in AW by 20-40% at stations with ~100-130mg PIC m -3. A novel approach for estimating PIC based on a theoretical relationship between diffuse attenuation and irradiance reflectance is also described.

The utility of photopigments and absorption signatures to detect and enumerate the red tide dinoflagellate, Gymnodinium breve, was evaluated in laboratory cultures and in natural assemblages. The carotenoid, gyroxanthin-diester, was an adequate biomarker for G. breve biomass; water-column concentrations corresponded with cell standing crops and chlorophyll a concentrations during bloom events in Sarasota Bay, Florida. Unlike other carotenoids, the relative abundance of gyroxanthin-diester did not change throughout a range of physiological states in culture and the gyroxanthin-diester: chlorophyll a ratio exhibited little variability in a natural assemblage during bloom senescence. Stepwise discriminant analysis indicated that wavelengths indicative of in vivo absorption by accessory chlorophylls and carotenoids could correctly discern spectra of the fucoxanthin-containing G. breve from spectra of peridinin-containing dinoflagellates; a diatom, a haptophyte, and a prasinophyte. With the use of a similarity algorithm, the increasing contribution of G. breve was discerned in absorption spectra (and corresponding fourth-derivative plots) for hypothetical mixed assemblages. However, the absorption properties of chlorophyll c-containing algae vary little among taxa and it is difficult to discern the contribution of accessory chlorophylls and carotenoids caused by cell packaging. Therefore, the use of absorption spectra alone may not identify the contribution of a chlorophyll c-containing taxon to the composite spectrum of a mixed assemblage. This difficulty in distinguishing among spectra can be minimized by using the similarity algorithm in conjunction with fourth-derivative analysis.

We compared the impact of structural changes in the light-harvesting machinery of two bloom-forming dinoflagellates (Prorocentrum minimum and Heterocapsa pygmaea) by quantifying photophysiological changes in order to define the alternative mechanisms of photoacclimation. There are species-specific and photoacclimative differences in the abundance and composition of functional light-harvesting complexes (including photosystem 1- and 2-enriched bands) which are reflected in spectral changes in absorption, and photosystem 2 (PS2) fluorescence excitation spectra of whole cells, thylakoid micelles, and discrete photosynthetic pigment-protein complexes. DCMU-induced variations in fluorescence excitation spectra are evident in whole cells but not in isolated thylakoid micelles or functional chromoproteins; such variations indicate that intracellular self-shading which causes variable fluorescence is eliminated in subcellular preparations. We developed a scaling procedure of PS2-related in vivo fluorescence excitation spectra relative to Chl a-specific absorption coefficients and used the chromoprotein differences to illustrate how the chromoprotein composition alters cellular fluorescence properties. We also examined the energy transfer efficiency of photosynthetic pigments and the photoprotective role and location of diadinoxanthin.

The spectral light absorption and fluorescence excitation spectra from thalli (in vivo) and thylakoid micelles (no intracellular self-shading) from the macroalgae Laminaria digitata (L.) Edmonson, Palmaria palmata (L.) Kuntze, and Ulva sp. were examined. In all the examined species, the intracellular self-shading (i.e. the package effect) was highly significant to the extent that absorption peaks related to individual pigments were significantly suppressed. Thus, for studies related to taxonomy and physiology, “unpacked”spectra may be more informative. Thylakoid micelle preparations offer opportunities to examine more closely species-specific differences in the packaging effect, light harvesting and utilization, and pigmentation. As well, the thylakoid micelles, when analyzed with biochemical assays or fluoromtry, may provide insight into components of the photosynthetic machinery that are specific to different classes of mncroalgne. We present the Chl a-specific absorption coefficients and the corresponding fluorescence excitation spectra of macroalgal thylakoid micelles for the three species.

Bathycoccus prasinos Eikrem et Throndsen exhibited a complex carotenoid distribution pattern including the carotenes β,β-carotene (0.8% of total carotenoids) and β, ° Carotene (0.4%) and several xanthophylls. These were prasinoxanthin (49% of total carotenoids), micromonal (16%), neoxanthin (14%), uriolide (7%), violaxanthin (0.8%), 31-dehydrouriolide (0.8%), dihydrolutein (0.1%), two partly characterized esterified carotenols (together 10%), and five minor unidentified carotenols (together 2%). The identifications were based on high-performance liquid chromatography (HPLC), thin-layer chromatography (TLC), visible spectroscopy (VIS), and mass spectra (MS) and in part on 1H nuclear magnetic resonance (NMR), circular dichroism (CD), and chemical derivatization. The carotenoid composition of B. prasinos was related to that of other prasinoxanthin / uriolide / micromonal-producing prasinophytes (Mantoniella squamata, Micromonas pusilla, and Pseudoscourfieldia marina). The relative distribution of chlorophylls (w/w) were chlorophyll a (chl a; 63%), chl b (31%), and an unknown chl c-like chlorophyll (7%) with spectral characteristics similar to magnesium 2,4-divinylphaeoporphyrin a, monomethyl ester, compatible with other prasinophytes. The chemosystematic data and ultrastructural characteristics for the order Mamiellales are discussed. We conclude that HPLC studies alone are insufficient for the identification and characterization of the carotenoids, including the minor carotenoids essential for biosynthetic/chemosystematic considerations.

The pigmentation and corresponding in vivo and in vitro absorption characteristics in three different deep-water coral species: white and orange Lophelia pertusa, Paragorgia arborea and Primnoa resedaeformis, collected from the Trondheimsfjord are described. Pigments were isolated and characterized by High-Performance Liquid Chromatography (HPLC) analysis and High-Performance Liquid Chromatography Time-Of-Flight Mass Spectrometer (LC-TOF MS). The main carotenoids identified for all three coral species were astaxanthin and a canthaxanthin-like carotenoid. Soft tissue and skeleton of orange L. pertusa contained 2 times more astaxanthin g−1 wet weight compared to white L. pertusa. White and orange L. pertusa were characterized with in vivo absorbance peaks at 409 and 473 nm, respectively. In vivo absorbance maxima for P. arborea and P. resedaeformis was typically at 475 nm. The shapes of the absorbance spectra (400–700 nm) were species-specific, indicated by in vivo, in vitro and the corresponding difference spectra. The results may provide important chemotaxonomic information for pigment when bonded to their proteins in vivo, bio-prospecting, and for in situ identification, mapping and monitoring of corals.

Abstract. The hypothesis that predators are less willing to attack dense swarms when far from cover was tested. Transparent cell compartments containing different densities of the prey, Daphnia magna, were placed either near to or far from a refuge for the predator, and two either hungry or satiated three-spined sticklebacks, Gasterosteus aculeatus, were allowed to attack the cell compartment. The trade-off between feeding maximization and predator avoidance in sticklebacks varied, depending on distance to cover, hunger level and the distance to the other fish. Hungry fish and the satiated fish in the safe areas were willing to risk feeding in confusing densities of prey (as in swarms), while satiated fish far from the cover were not. Hence, zooplankton swarms would benefit from swarming in areas where planktivorous fish are at most risk from predators.

International audience; This chapter reviews the nature of pigment variations in phytoplankton in response to changes in light regime (irradiance, spectral composition and daylength). These changes belonging to processes called acclimation and/or adaptation maximize the evolutionary fitness of a species, within the constraints set by the environmental conditions (Raven and Geider, 2003). In general, adaptation indicates long-term evolutionary outcome based on the genes a given species obtains (genetic adaptation) while acclimation denotes adjustments in response to variation in key-environmental variables (physiological acclimation).Photo-acclimation corresponds to a mosaic of processes involving many cellular components and occurring over a broad range of time scales, from seconds to days. These processes, covering many physiological, biochemical, biophysical and biological changes, allow the optimization of cell activities, such as photosynthesis, respiration, growth and division when faced with changing irradiance (e.g., Herzig and Dubinsky, 1993; Anning et al., 2000; Raven and Geider, 2003). This is an important issue in phytoplankton ecology because of the fluctuating light environment experienced by pelagic algae, related to daylight variations together with the exponential decrease of light and the vertical – active or passive – movements of algae along the water column. In order to cope with these never-ending fluctuations in light-regime, marine phytoplankton can adjust their pigment pool, which is mainly constituted by two functional categories, namely pigments used for light harvesting and for photoprotection. Many accessory pigments constituting the light-harvesting complexes are photosynthetically active i.e. they are able to transfer the energy absorbed from sunlight to the photosynthetic reaction centers (RC) of photosystems (PS) II and I. They are called light harvesting pigments and include the photosynthetic carotenoids. However, some carotenoids are not involved in photosynthesis and do not transfer the absorbed energy to the RC. These non-photosynthetically active carotenoids are also called photoprotective carotenoids (PPC). The function and dynamics of long-term (hours-days) and short-term (minutes-hours) photo-acclimation are described in the following two sections (4.4.1 and 4.4.2, respectively). The long-term photo-acclimation response mainly consists in changes of structure and composition of the photosystems while the short-term photo-acclimation process mainly concerns the xanthophyll cycle (XC) activation and the associated non-photochemical fluorescence quenching (NPQ). In the third section (4.4.3), the ecophysiological variability of XC and its use as a biological tracer in oceanographic studies is reported.

Introduction The absorption of light by algal pigments determines the cellular absorption of phytoplankton and thus contributes to the in situ optical signatures of coastal and offshore waters. This is the basis of a range of bio-optical approaches used for monitoring phytoplankton distribution (taxa and biomass) and is the focus of this chapter. Details regarding bio-optical signatures of phytoplankton and their spectral absorption, scattering and fluorescence characteristics are covered in Chapter 13, this volume. Details of how phytoplankton adjust their pigments in response to variation in light climate are reviewed in Chapter 11, this volume. Phytoplankton blooms cover spatial scales that vary from patches of 1 m 2 to large blooms covering more than 1 × 10 6 km 2 (Franks, 1997; Smyth et al ., 2004; Schofield et al ., 2008). Related to the spatial scale is the temporal variability of these blooms (from minutes to years), depending on the physical and biological processes at a given location. The development of techniques for monitoring phytoplankton blooms at different geographical and temporal scales has evolved rapidly in recent years (Kahru and Brown, 1997; Schofield et al ., 1999; Babin et al ., 2008). Because of the wide range in scale, different methods and approaches (different sensors and corresponding platforms) are needed for monitoring water masses and associated phytoplankton blooms as a function of environmental change (i.e. temperature, salinity, circulation and light regime), biogeochemical cycling, eutrophication, ocean acidification and pollution. Globally, monitoring of phytoplankton bloom dynamics is important to estimate changes in primary productivity affecting carbon and nutrient cycling in the world oceans.