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Climate change and sea level rise are causing an increase in salinity in coastal salt marshes around the world. These changes may alter the germination dynamics of some halophytes, threatening their conservation. Our study area (Atlantic coast of the southwestern Iberian Peninsula) is currently being affected by sea level rise, and increases in sediment salinity have been recorded. We studied the germination responses during and after a wide range of imposed salinities (0-600 mM) of 5 Asteraceae species; 3 colonizing salt marshes (Artemisia caerulescens, Aster tripolium and Inula crithmoides) and 2 (Dittrichia spp.) inhabiting adjacent non-tidal environments. In addition, habitat characteristics (plant cover, sediment redox potential, electrical conductivity, pH, water content and bulk density) associated with each marsh species were measured and compared with the spatial distribution of the Asteraceae species in the field and their capacity to germinate at different salinities. The germination syndrome of Aster tripolium and Inula crithmoides was characterized as germinating in salinity ranging from fresh water to 600 mM salinity (36 ppt). The rare halophyte A. caerulescens and the 2 non-tidal Dittrichia species presented a germination syndrome based on no germination at high salinities and high recovery germination (55-80%). Considering the high sensitivity of A. caerulescens to salinity during germination, active conservation measures are recommended to promote its preservation in the Mediterranean Basin. These include creating new populations and promoting salt marsh connectivity to facilitate the processes of species mobility and marsh migration to uplands where sediment salinity is lower.

Current understanding of species capacities to respond to climate change is limited by the amount of information available about intraspecific variation in the responses. Therefore, we quantified between- and within- population variation in larval performance (survival, development, and growth to metamorphosis) of the shore crabCarcinus maenasin response to key environmental drivers (temperature, salinity) in 2 populations from regions with contrasting salinities (32-33 PSU: Helgoland, North Sea; 16-20 PSU: Kerteminde, Baltic Sea). We also accounted for the effect(s) of salinity experienced during embryogenesis, which differs between populations. We found contrasting patterns between populations and embryonic salinity conditions. In the Helgoland population, we observed a strong thermal mitigation of low salinity stress (TMLS) for all performance indicators, when embryos were kept in seawater. The negative effects of low salinity on survival were mitigated at increased temperatures; only at high temperatures were larvae exposed to low salinity able to sustain high growth rates and reduced developmental time, thereby metamorphosing with comparable levels of carbon and nitrogen to those reared in seawater. By contrast, larvae from the Kerteminde population showed a detrimental effect of low salinity, consistent with a maladaptive response and a weak TMLS. Low salinity experienced during embryogenesis pre-empted the development of TMLS in both populations, and reduced survival for the Kerteminde population, which is exposed to low salinity. Our study emphasises the importance of evaluating species responses to variation in temperature and salinity across populations; the existence of maladaptive responses and the importance of the maternal habitat should not be underestimated.

In estuaries, fluctuating environmental conditions exact strenuous physiological demands on the fishes that inhabit these oft-impacted areas, including the Critically Endangered delta smeltHypomesus transpacificusin California (USA). Using an archive of otoliths spanning 2011-2019, we examined how growth rates of wild subadult delta smelt vary ontogenetically, regionally, and in relation to variation in the physical environment during late-summer and fall in the upper San Francisco Estuary. Recent growth rates were quantified using otolith increment analysis and modeled as functions of both intrinsic (age) and extrinsic (temperature, salinity, clarity, and region) factors using a suite of generalized additive models. Age explained 60% of the variation in log10-transformed growth rates, which peaked at 50-80 d post hatch. Overall, age-adjusted growth rates declined at temperatures >20°C, increased with practical salinity values of 0-4, and exhibited interactive patterns with water clarity. Growth rates appeared highest in the West and Central Delta, and lowest in the North Delta, also corresponding with patterns in environmental conditions. Here, we provide new evidence for how vital rates of wild delta smelt vary spatially and in relation to abiotic environmental variation. Such otolith-based growth reconstructions often provide the first direct look at how the vital rates of wild fish respond to environmental variationin situ, and how future changes are likely to affect the dynamics of wild populations.

Environmental history (regimes of water quality to which an organism has been exposed in the past) may influence how the physiology of eastern oysters Crassostrea virginica responds to future environmental conditions caused by climate change. Previous research has examined environmental history in a 1-dimensional framework, failing to capture environmental history complexity through space and time. In this study, we examined environmental history as a multi-faceted parameter, incorporating abiotic water quality components, such as temperature, pH, and salinity, that differ among locations. We also assessed how different lengths of environmental histories, defined as proximal and distal, affected oyster physiology and stress response. Finally, we compared the relative influence of abiotic components of environmental history on oyster physiology. We found that physiology and stress response are differentially affected by proximal and distal environmental history, demonstrating the importance of examining environmental history as a multi-faceted and dynamic parameter. Specifically, distal environmental history primarily influenced condition index and total antioxidant potential, while proximal environmental history primarily influenced glycogen content. Salinity of distal environmental history significantly shaped condition index, establishing salinity as a principal factor when considering acclimatization to variable environments. No water quality components were significant influences on glycogen and total antioxidant potential, providing opportunities for research on other components of environmental history. Identifying the temporal portion of oysters’ environmental history that influences physiology supports future efforts to predict population tolerance to climate change. Additionally, examining multiple abiotic and biotic components of environmental history can elucidate means of acclimatization to future environmental change.

The diversity of symbiotic dinoflagellate Symbiodiniaceae hosted by anthozoans is known to be driven by the environment where the hosts are found. This study examined how environmental variations (Palythoa tuberculosa. We monitored the dominant Symbiodiniaceae lineages within tagged P. tuberculosa colonies near the Hija River mouth and adjacent coastal reefs at Mizugama, Okinawa, Japan, between July 2016 and April 2018. Seven sites were chosen based on depth and distance from the river mouth, with 5 tagged colonies at each site. Water parameters of tidal pools (TPs) at the river mouth, especially temperature, were significantly different from other sites. Surprisingly, P. tuberculosa colonies at TPs were more resilient to bleaching during summers compared to colonies at other shallow sites. We observed different Cladocopium psbAncr lineages hosted by the tagged P. tuberculosa, with TPs colonies usually hosting one Cladocopium lineage (designated as lineage 4). Colonies from the deep sites and other shallow sites hosted mostly Cladocopium lineages 1 (generalist) and 2 (riverine specialist). Throughout the study period, the shallow colonies (included TPs) recorded higher rates of switching dominant Cladocopium lineages (mostly to lineage 1), whereas most deep colonies did not switch their dominant Cladocopium lineages. Our results show that Cladocopium lineage 1, previously reported as a generalist lineage in terms of environmental parameters, could also be an opportunist lineage during periods of host stress. Our study confirms that Cladocopium lineage flexibility likely helps the resilience of P. tuberculosa in such variable environments.

The Peruvian anchoveta Engraulis ringens is one of the most important commercial fishes along the Humboldt Current. Previous studies have shown that egg quality (volume, protein and lipid content) and hatching rates decrease during the spawning season, from the rainy winter to late spring. In this study, we assessed whether changes in atmospheric condition that led to an intense drought over a decade modified the freshwater river fluxes and seawater salinity at an E. ringens coastal spawning zone off central Chile (36° 30’ S), and determined if changes in salinity affect the hatching-gene expression, hatching-enzyme expression, and hatching success in eggs incubated at a range of salinities (27-35 psu) normally occurring during the reproductive season. Results showed that hatching-enzyme expression increased as the embryo developed. The highest expression of the hatching-enzyme gene and of the enzyme itself, along with hatching success were obtained at the lowest incubating salinity (27 psu). In the field, hatching success decreased from late winter to late spring, the start of the upwelling period at the end of the reproductive season. Thus, variations in salinity of the seawater during the spawning period are coincident with changes in gene expression of the hatching enzyme, the hatching enzyme expression, and hatching success. Spawning late in winter when rainfall is higher and seawater salinity in the coastal area is lower may increase hatching success, a reproductive strategy that might be affected by the observed climate changes and severe drought in central Chile.

Polar regions are facing rapid temperature increase. In Arctic fjord systems, increased temperatures result in hyposalinity caused by the melting of sea ice and glaciers and freshwater run-off. Additionally, enhanced freshwater discharge and intrusion of nutrient-rich Atlantic water may result in nutrient input in summer. Combined, these factors might have a strong impact on primary producers, such as the abundant kelp speciesSaccharina latissima, an important foundation species in Arctic shallow-water coastal ecosystems. We ran 2 short-term 2factor experiments with field samples from Kongsfjorden (Svalbard) to evaluate the impact of temperature increase in summer combined with hyposalinity (temperature × salinity) or nutrient enrichment (temperature × nutrients) on the physiological and biochemical status of ArcticS. latissima. In the temperature × salinity experiment, growth and maximum photosynthetic quantum yield of photosystem II (Fv/Fm) were generally not affected. Temperature increase resulted in increased C:N ratios, based on decreasing nitrogen assimilation. Overall, hyposalinity had no severe effect but resulted in lower phlorotannin concentrations. Growth andFv/Fmimproved with increasing temperatures and nutrient enrichment. The de-epoxidation state of the xanthophyll cycle and mannitol declined at higher temperatures. Regarding other biochemical response variables, nutrients had no major impact (temperature × nutrients). In conclusion, in line with its broad latitudinal distribution range and adaptability,S. latissimaproved to be highly resilient to changing abiotic drivers and will likely be promoted by warming in the future Arctic.

The establishment of the piscivorous lionfishPteroisspp. in the Western Atlantic and wider Caribbean is a well-documented example of a successful marine invasion. Recently, lionfish have been shown to colonise a wide range of ecosystems and tolerate a wider range of salinities than previously thought. In the present study, lionfish were maintained in aquaria under differing salinity treatments (10, 20 and 37 psu) similar to those they might experience in an estuarine ecosystem. The effects of long-term hyposaline exposure on growth, metabolic rate, maximum food consumption and digestion were examined. Consistent with previous studies, lionfish were able to survive in hyposaline conditions for extended periods of time. However, lionfish in the most hyposaline treatment (10 psu) exhibited reduced growth under low food conditions, lower maximum metabolic rate, lower aerobic scope, lower maximum food consumption, took longer to digest a standardized meal size and occupied a greater percentage of their aerobic scope during digestion. Results suggest that (1) given the ability of lionfish to tolerate low salinity, updated range expansion models should incorporate salinity data to improve accuracy of predicted range expansion and (2) the invasion of lionfish into low salinity ecosystems, although a serious concern, will not likely lead to the same level of population increase observed for coral reef habitats due to the physiological costs associated with living in low salinities.

The abiotic environment varies continuously at a variety of temporal scales. While this variation is known to be ecologically important, multiple scales of variability are rarely explicitly considered in ecological studies. Here, we combine field observations and laboratory experiments to determine the individual and population level effects of short-term (tidal) and longer-term (seasonal and interannual) salinity variation on the dogwhelkNucella lamellosain the Strait of Georgia, British Columbia, Canada. The Fraser River heavily influences surface salinity in the Strait of Georgia, which varies with season, depth, and distance to the river mouth. At low salinity sites,N. lamellosapopulation size decreased following high outflow years, with fewer juveniles present, as opposed to high salinity sites, which had higher population densities in all years. Sustained salinity exposure in the laboratory caused developmental delay of encapsulated embryos and complete mortality at 9 and 12 psu. Juvenile dogwhelks (N. lamellosato survive otherwise low salinity conditions for considerably longer. Overall, our results suggest that seasonal and interannual variation in salinity have a profound influence onN. lamellosapopulations and that shorter-scale fluctuations can moderate these seasonal and interannual effects. It is likely that similar multi-scale environmental effects will determine survival and population dynamics in many species.

Abiotic factors can influence the distribution of organisms through physiological tolerance limits and by affecting their sensory performance in critical life history functions such as foraging or predator avoidance. In estuaries, salinity and turbidity directly influence the distribution of organisms but the indirect, synergistic effects of these factors on trophic interactions and community structure remain obscure. We investigated the effects of salinity and turbidity on oyster reef communities by comparing oyster reef community structure in low vs. high turbidity in consecutive years that varied considerably in rainfall and ambient salinity levels. Turbidity had significant effects in both 2016 and 2017 by interfering with fish foraging ability and consumption. In turbid sites, fish predation decreased by ~21%, crab mesopredators were 11% larger and nearly 5 times more abundant due to reduced top-down control by fish, and oyster reef biodiversity was 12% lower. In 2016, oysters were 350% less abundant in sites with abundant crab predators. However, in 2017, salinity increased, facilitating a new predator (oyster drills Stramonita haemastoma) to emerge onto reefs, and oysters were 7 times less abundant in sites with oyster drills despite having fewer crab predators. Thus, salinity and turbidity can indirectly affect food webs by facilitating different predators and influencing their sensory performance. Turbidity had significant effects on estuarine food webs regardless of salinity levels, and like salinity, turbidity should also be considered in oyster reef restoration and management of estuarine ecosystems.

Otolith chemistry is frequently employed in the reconstruction of fish environmental histories. While some elements have been strongly correlated with environmental factors (e.g. salinity, temperature, water chemistry), others may not indicate exogenous factors and simply add endogenous variability to a data set. Several commonly assessed elements were previously identified as being only present in the proteinaceous fraction of endolymph from black bream Acanthopagrus butcheri, suggesting that the choice of elements in otolith multi-elemental fingerprinting could influence their utility as natural environmental markers. To test this hypothesis, we performed several cluster analyses based on different sets of trace element data extracted from both the core and larval region of otoliths of juvenile black bream. We clustered in 3 different ways: (1) all elements analysed; (2) elements identified as being primarily in the salt fraction of the endolymph (i.e. inorganic); and (3) elements identified as being associated with the protein fraction of the endolymph. We subsequently assessed the power of the resulting clusters to resolve cohort identity and/or collection location based on differences in otolith chemistry using multinomial logistic regression. Our results indicate that clustering based solely on salt-fraction elements is best for resolving spatio-temporal variability in spawning sources and larval nursery habitats of black bream.

Geochemical signatures in calcified structures of marine organisms have been widely used as environmental markers and natural tags, reflecting seawater characteristics and allowing the study of larval dispersal patterns. However, the role of environmental, biological and physiological factors in the incorporation of trace elements in carbonate structures is still not fully elucidated. Here, we investigated the effects of temperature and salinity on the incorporation of several elements (23Na, 24Mg, 48Ca, 55Mn, 63Cu, 88Sr and 137Ba) in larval shells of Mytilus galloprovincialis. Larvae were cultured in the laboratory under different temperatures (12, 17, 20°C) and salinities (26, 32, 37) in a factorial design. Results showed an enrichment of Na/Ca, Sr/Ca and Cu/Ca ratios in shells under low salinity and high temperature treatments. Mg incorporation in the shell was also affected by temperature. Mn/Ca and Ba/Ca were the only elements with no clear relationship to the factors tested, indicating lower physiological control and/or alternative pathways for incorporation. Our results suggest the need for careful interpretation in the use of geochemical structures as environmental proxies due to the high physiological control over shell deposition. Nonetheless, temperature and salinity effects on shell composition can contribute to finding differential tags between habitats with similar elemental availability. Understanding the underlying mechanisms of element incorporation into larval shells constitutes crucial baseline information to interpret environmental signatures in ecological studies.

In the 1930s, outbreaks of the wasting disease pathogen Labyrinthula zosterae caused a severe reduction of the eelgrass Zostera marina meadows in the Atlantic Ocean. Many surviving populations were found in low-salinity environments, and low-salinity environments have therefore been hypothesized to act as a refuge for eelgrass against L. zosterae infection. Here, we investigated L. zosterae pathogen load and wasting disease symptoms in eelgrass over a similar to 970 km salinity gradient (6-25 PSU) along the Swedish coast. Furthermore, laboratory infection experiments and studies of inhibitory compounds were carried out to investigated whether resistance against the pathogen is correlated to differences in natural pathogen pressure among eelgrass populations. The degree of L. zosterae infection was positively correlated to salinity and the pathogen was absent in several of the eelgrass meadows in lower salinity (7-8 PSU). However, a low L. zosterae pathogen load was also found in some eelgrass populations in the lowest salinity (6 PSU). No correlation between resistance and pathogen pressure in situ was detected, and all eelgrass shoots produced chemical compounds that inhibited L. zosterae growth. These results imply that positive correlations between L. zosterae and salinity are not due to eelgrass resistance, but rather to the poor ability of L. zosterae to cope with low salinity. However, our results also indicate that some strains of L. zosterae may adapt to low salinity, and therefore there may also be a risk of wasting disease outbreaks in low-salinity eelgrass meadows, in contrast to what so far has been the general hypothesis.

Soft-shelled clams, Mya arenaria, and razor clams, Tagelus plebeius, in Chesapeake Bay have been in decline since the 1970s, with severe declines since the early 1990s. These declines are likely caused by multiple factors including warming, predation, habitat loss, recruitment limitation, disease, and harvesting. A bivalve survey was conducted in Chesapeake Bay to examine influential factors on bivalve populations, focusing on predation (crab, fish, and cownose rays), habitat type (mud, sand, gravel, shell, or seagrass), environment (temperature, salinity, and dissolved oxygen), recruitment, and disease. M. arenaria and T. plebeius were found more often in more-complex habitats such as seagrass or shell than any other habitat. Pulses in bivalve density associated with recruitment were attenuated through the summer and fall when predators are most active, indicating that predators likely influence temporal dynamics in these species. Mya arenaria, which is near the southern extent of its range in Chesapeake Bay, was negatively associated with high water temperatures. Recruitment of M. arenaria in Rhode River, MD, declined steadily between 1980 and 2016. Infection by the parasitic protist Perkinsus sp. was associated with stressful environmental conditions, bivalve size, and environmental preferences of Perkinsus sp, but was not associated with bivalve densities. It is likely that habitat loss, low recruitment, and predators are major factors keeping T. plebeius and M. arenaria at low densities in Chesapeake Bay. Persistence at low densities may be facilitated by complex habitats, whereas further reductions in habitats such as seagrass could result in local extinction of these important bivalve species.

Early-developed polyps of the giant jellyfish Nemopilema nomurai that are sexually produced during the rainy season form the principal recruitment for benthic population stages, regulating the mass outbreaks of medusae that occur in east Asian marginal seas. Their survival, development and subsequent asexual reproduction are likely facilitated by hyposaline seawater and potentially enhanced micro-zooplankton around the estuaries that comprise the major nurseries of medusae. In this study, 8-tentacled polyps that developed from planulae were incubated at 11 salinities from low to high (8, 11, 13, 15, 18, 20, 23, 25, 28, 31, 33) with 3 feeding frequencies (once every 3 d, once every 9 d, unfed; Brachionus plicatilis concentration: 0.16 mg C l(-1)) at a constant temperature (19 degrees C). Survival rate of early-developed polyps increased 3-fold at salinities 11 to 20, > 80% greater than at salinities 25 to 33. The composition of fully developed polyps, somatic growth, and podocyst diameter positively depended on food supply, except at salinity 8. The potential podocyst production of polyp colonization reached normal peak at salinity 20 in the group that was fed once every 3 d. Excystments were significantly restricted at salinity < 20. These findings confirm that estuarine areas with salinities from 11 to 20 are appropriate for N. nomurai polyp colonization, where prospectively increasing micro-zooplankton supply rooted in frequent eutrophication may benefit polyps. An asexual reproduction strategy also corresponded with autumn salinity fluctuations. The intensity of diluted water and monsoonal rainfall, as well as plankton supply around the estuaries in autumn may fundamentally affect polyp abundance and size, determining the population size of medusae in the following spring.

The potentially lethal Chironex fleckeri (Class Cubozoa) inhabits estuarine and nearshore coastal waters in the western Pacific. The spatial scales of connectivity between C. fleckeri populations are poorly understood. Biophysical modelling of Port Musgrave, a 17 × 21 km shallow bay in tropical Australia, was used to investigate the potential for connections between populations separated by medium (10s of km) to small (100s of m) spatial scales. We measured the swimming speeds and orientations of medusae ranging in size from 4 to 12 cm interpedalial distance (the distance between two adjacent corners on the bell of the medusae). Medusae swam longshore at average speeds (5.3 ± 3.5 cm s-1 SD) that exceeded the local average current speeds (2.7 ± 2.4 cm s-1). These and other ecological data were used to parameterise the biophysical model. No medusae modelled as passive were advected from the bay in 14 d

We assessed geographic patterns of abundance of the isopodExcirolana braziliensis across its whole distribution range in the context of the abundant centre hypothesis (ACH). We also evaluated auxiliary y potheses to the ACH involving habitat availability and suitability. We compiled species abundance and occurrence information on 139 Pacific and Atlantic sandy beaches of the Americas. Abundance patterns were contrasted against 5 hypothetical distribution models. Habitat availability (sandy beach along the coast), and the role played by grain size on isopod abundance were analysed. Maximum entropy niche modelling based on primary production, salinity, water temperature and tidal range data was used to estimate trends in habitat suitability. E. braziliensis abundance peaked at the 2 edges of its range on the Atlantic coast and towards the centre of its range on the Pacific coast. Congruently, the niche model predicted very low habitat suitability at the centre of the species’ range on the Atlantic coast. Primary production was the main contribution to the model (74.8%). The highest abundances were found in fine sediments (0.20 mm). Support for the ACH forE. braziliensis was found only for the Pacific coast, whereas habitat suitability and availability together with local in-beach morphodynamics accounted for deviations from ACH predictions in the Atlantic. The highest abundances registered in upwelling areas and on beaches with fine sands highlight the primary role played by regional and local conditions over geographic location.