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In the North Patagonian fjord region, the cold-water coral (CWC) Desmophyllum dianthus occurs in high densities, in spite of low pH and aragonite saturation. If and how these conditions affect the energy demand of the corals is so far unknown. In a laboratory experiment, we investigated the carbon and nitrogen (C, N) budget of D. dianthus from Comau Fjord under three feeding scenarios: (1) live fjord zooplankton (100 2,300 mm), (2) live fjord zooplankton plus krill (>7 mm), and (3) four-day food deprivation. In closed incubations, C and N budgets were derived from the difference between C and N uptake during feeding and subsequent C and N loss through respiration, ammonium excretion, release of particulate organic carbon and nitrogen (POC, PON). Additional feeding with krill significantly increased coral respiration (35%), excretion (131%), and POC release (67%) compared to feeding on zooplankton only. Nevertheless, the higher C and N losses were overcompensated by the threefold higher C and N uptake, indicating a high assimilation and growth efficiency for the krill plus zooplankton diet. In contrast, short food deprivation caused a substantial reduction in respiration (59%), excretion (54%), release of POC (73%) and PON (87%) compared to feeding on zooplankton, suggesting a high potential to acclimatize to food scarcity (e.g., in winter). Notwithstanding, unfed corals `lost' 2% of their tissue-C and 1.2% of their tissue-N per day in terms of metabolism and released particulate organic matter (likely mucus). To balance the C (N) losses, each D. dianthus polyp has to consume around 700 (400) zooplankters per day. The capture of a single, large krill individual, however, provides enough C and N to compensate daily C and N losses and grow tissue reserves, suggesting that krill plays an important nutritional role for the fjord corals. Efficient krill and zooplankton capture, as well as dietary and metabolic flexibility, may enable D. dianthus to thrive under adverse en

Ocean warming is a major threat for coral reefs causing widespread coral bleaching and mortality. Potential refugia are thus crucial for coral survival. Exposure to large-amplitude internal waves (LAIW) mitigated heat stress and ensured coral survival and recovery during and after an extreme heat anomaly. The physiological status of two common corals, Porites lutea and Pocillopora meandrina, was monitored in host and symbiont traits, in response to LAIW-exposure throughout the unprecedented 2010 heat anomaly in the Andaman Sea. LAIW-exposed corals of both species survived and recovered, while LAIW-sheltered corals suffered partial and total mortality in P. lutea and P. meandrina, respectively. LAIW are ubiquitous in the tropics and potentially generate coral refuge areas. As thermal stress to corals is expected to increase in a warming ocean, the mechanisms linking coral bleaching to ocean dynamics will be crucial to predict coral survival on a warming planet.

Many coral reefs in the Caribbean experienced substantial changes in their benthic community composition during the last decades. This often resulted in phase shifts from scleractinian coral dominance to that by other benthic invertebrate or algae. However, knowledge about how the related role of coral-algae contacts may negatively affect corals is scarce. Therefore, benthic community composition, abundance of algae grazers, and the abundance and character of coral-algae contacts were assessed in situ at 13 Belizean reef sites distributed along a distance gradient to the Belizean mainland (12–70 km): Mesoamerican Barrier Reef (inshore), Turneffe Atoll (inner and outer midshore), and Lighthouse Reef (offshore). In situ surveys revealed significantly higher benthic cover by scleractinian corals at the remote Lighthouse Reef (26–29%) when compared to the other sites (4–19%). The abundance of herbivorous fish and the sea urchin Diadema antillarum significantly increased towards the offshore reef sites, while the occurrence of direct coral-algae contacts consequently increased significantly with decreasing distance to shore. About 60% of these algae contacts were harmful (exhibiting coral tissue damage, pigmentation change, or overgrowth) for corals (mainly genera Orbicella and Agaricia), particularly when filamentous turf algae were involved. These findings provide support to the hypothesis that (turf) algae-mediated coral damage occurs in Belizean coastal, near-shore coral reefs.

Coral reefs are facing rapidly changing environments, but implications for reef ecosystem functioning and important services, such as productivity, are difficult to predict. Comparative investigations on coral reefs that are naturally exposed to differing environmental settings can provide essential information in this context. One prevalent phenomenon regularly introducing alterations in water chemistry into coral reefs are internal waves. This study therefore investigates the effect of large amplitude internal waves (LAIW) on primary productivity in coral reefs at the Similan Islands (Andaman Sea, Thailand). The LAIW-exposed west sides of the islands are subjected to sudden drops in water temperature accompanied by enhanced inorganic nutrient concentrations compared to the sheltered east. At the central island, Ko Miang, east and west reefs are only few hundred meters apart, but feature pronounced differences. On the west lower live coral cover (-38%) coincides with higher turf algae cover (+64%) and growth (+54%) compared to the east side. Turf algae and the reef sand-associated microphytobenthos displayed similar chlorophyll a contents on both island sides, but under LAIW exposure, turf algae exhibited higher net photosynthesis (+23%), whereas the microphytobenthos displayed reduced net and gross photosynthesis (-19% and -26%, respectively) accompanied by lower respiration (-42%). In contrast, the predominant coral Porites lutea showed higher chlorophyll a tissues contents (+42%) on the LAIW-exposed west in response to lower light availability and higher inorganic nutrient concentrations, but net photosynthesis was comparable for both sides. Turf algae were the major primary producers on the west side, whereas microphytobenthos dominated on the east. The overall primary production rate (comprising all main benthic primary producers) was similar on both island sides, which indicates high primary production variability under different environmental conditions. © 2

It has been hypothesized that endolithic photo- autotrophs inside the skeleton of cold-water corals may have a mutualistic relationship with the coral host posi- tively affecting coral calcification. This study investigated the effect of endolithic photo-autotrophs on the apical septal extension of the cold-water coral Desmophyllum dianthus at Fjord Comau, southern Chile (42.41°–42.15°S, 72.5°W). The fluorescent staining agent calcein was used to document the linear apical extension of septae for a period of one and a half years between 2006 and 2007. The results showed a severe reduction in extension rates asso- ciated with the presence of endolithic photo-autotrophs. Infested individuals grew about half as fast as non-infested polyps with a median value of 1.18 lm day-1 compared to 2.76 lm day-1. Contrary to the initial hypothesis, these results point toward a parasitic relationship between D. dianthus and its endolithic photo-autotrophs potentially impairing coral fitness. However, further data on physio- logical parameters and other aspects of the calcification process are necessary to confirm these findings.

The solitary cosmopolitan cold-water coral Desmophyllum dianthus (Esper, 1794) (A, scale bar approximately 1 cm) occurs as a deep-water emergent species in Patagonian fjords, Chile, and can form extensive banks (Försterra et al. 2005). This coral functions as a bioengineer by providing a 3D habitat for a diverse benthic community (Försterra et al. 2005). With skeletal growth, the living tissue is retracted by the organism to the upper part of the calyx, leaving the lower skeleton uncovered. Endolithic algae are then able to enter the tissue covered skeleton from below and start to encrust the tissue covered part of the skeleton (Försterra et al. 2005, 2008). They are visible as a greenish coat on the skeleton (A). The algae are able to bore into the skeleton (Försterra et al. 2005) and thus could interfere with the coral’s calcifying process. This process could result in a parasitic behavior (Försterra et al. 2012) rather than the previously hypothesized (Försterra and Häussermann 2008) symbiotic or even mutualistic relationship. This infection by algae may be the primary reason for the peculiar behavior we observed on several specimens both in situ (A) and in our aquaria system (B–D, scale bar approximately 1 cm). After an acclimatization time in our aquaria system, wild collected corals were well adapted and well fed, and secondarily expanded their tissue toward their lower skeleton (about 1 cm in 4 mo, CJ and GMS pers obs), recovering an area that had been without any tissue. Concomitantly, the corals everted their mesenterial filaments between this re-entered outer-skeleton and the covering tissue layer (A, B; C, D: both enlargements of B). During the eversion of the mesenterial filaments the new tissue generally appeared unusually pleated (C, D) in contrast to a less common smooth tissue surface (A). This was not a short-term or rare mechanism: corals maintained this behavior in the aquaria over multiple months. Several tropical coral species are known to eject

Cold-water corals are known to grow much slower than their tropical counterparts. However, this assumption is mainly based on laboratory measurements exposing specimens to conditions that differ from their natural environments. The cosmopolitan scleractinian Desmophyllum dianthus forms dense banks below 18min northern Patagonia, Chile. So as to measure in situ growth rates of this cold-water coral, specimens were collected from two sites, weighed and deployed on holders in their natural headlong orientation at the respective collecting site. Corals exhibited a calcium carbonate (CaCO3) mass increase of 5.44+/-3.45 (mg (cm2 projected calyx area)^-1 day^-1) after 2 weeks, equivalent to a mass gain of 0.25+/-0.18 s.d. % day^-1. In comparison, D. dianthus specimens from the same collection sites maintained in an on-site flow-through aquarium system showed lower growth rates that were third of the in situ rates. In situ CaCO3 precipitation of D. dianthus extrapolated for 1 year (kg m^2 year^-1) displays the same order of magnitude as reported for massive growing tropical scleractinians, e.g. Porites sp.

Increasing dissolution of anthropogenic-released carbon dioxide into the world’s oceans is causing ocean acidification (OA). OA is thought to negatively affect most marine-calcifying organisms, notably cold-water corals (CWC), which may be especially sensitive due to the deep and cold waters they normally thrive in. However, the impact of OA on CWC is difficult to predict. Recorded distributions of CWC are rarely linked to in situ water chemistry, and the boundaries of their distributions are not clearly defined. The fjord Comau in Chilean Patagonia features pronounced pH gradients, and up to 0.5 pH units have been recorded both vertically (at some sites within 50 m depth) and less distinct horizontally (from head to mouth). The cosmopolite coral Desmophyllum dianthus grows along the course of the fjord and of the entire pH range. It occurs in shallow depths (below 12 m, pH 8.1) as part of a deep-water emergence community, but also in 225 m depth at a pH of 7.4. Based on pH and totalalkalinity, data calculations of the associated carbonate chemistry revealed that this CWC thrives commonly close the aragonite (the orthogonal crystal form of calcium carbonate, the mineral structure of coral skeletons) saturation horizon and even below. This suggests a high adaptation potential of D. dianthus to adjust its calcification performance to conditions thermodynamically unfavourable for the precipitation of aragonite.

Magellania venosa, the largest recent brachiopod, occurs in clusters and banks in high abundances of up to 416 ind m-2 in the fjord Comau, northern Chilean fjord region. At some stations, it numerically dominates the subtidal benthic community below 15 m depth, competing for space with the mytillid Aulacomya atra. To determine the question why Magellania venosa is a successful competitor, the brachiopod’s in situ growth rate was studied and its overall growth performance was compared with that of other brachiopods and mussels. The length growth was measured between Februay 2011 and March 2012 after mechanical tagging and Calcein staining. Settlement and juvenile growth were determined from recruitment tiles installed in 2009 and from subsequent photocensus. Growth of Magellania venosa is best described by the general von Bertalanffy growth function, with a maximum shell length (L∞) of 71.53 mm and a Brody growth constant (K) of 0.336 yr-1. The growth rate is the highest recorded for a rynchonelliform brachiopod. Maximal individual somatic production (PInd) is 0.29 g AFDM ind-1 yr-1 at 42 mm shell length and annual production ranges from 1.28 – 89.25 g AFDM yr-1 m-2. The high shell growth rate of Magellania venosa, together with its high overall growth performance may explain the high abundances of this brachiopod in the fjord Comau. However, the somatic production per biomass of the population ( -ratio) is low (0.535) and Magellania venosa may play a minor role in the food chain. Settling behaviour indicates that Magellania venosa is a pioneer species with low juvenile mortality. The brachiopod-bivalve coexistence suggests that neither the presence of potential brachiopod predators nor space competitors (i.e. mytiilids) affect the survival of the brachiopod population.

The Andaman Sea experienced extensive coral bleaching events in the years 1991, 1995 and 2003 but showed no significant mortality during these events. In 2010 an extremely severe bleaching event was monitored on several reefs along an offshore cross-shelf island gradient and data revealed up to 100% bleached coral colonies during the peak temperature phase, yet with some reefs showing considerably lower bleaching intensities. Even, ten months after the peak temperature stress most of the reefs appeared stressed starting slowly to recover, with again some reefs recovering faster. Additionally, environmental parameters as temperature and sedimentation rate were measured. A characteristic of the region is the existence of large amplitude internal waves (solitons) approaching the islands from the west, which introduces pulses of cold, nutrient-rich and turbid water into the shallow reef areas. High-resolution temperature records displayed that these phenomena prevailed during the temperature rise and served as cold showers during temperature highs. The current Andaman Sea bleaching monitoring showed the importance of fully capturing the environmental background especially underwater temperature regime and how it influences coral reef ecosystems. However, factors such as species composition, sedimentation, and biological invaders can additionally positively or negatively impact reefs during bleaching events and make predictions even more complex. Regions with reoccurring temperature anomalies providing cold water pulses could be important for coral reef recovery to serve as refuges replenishing adjacent severely damaged reefs with new recruits. The knowledge of such environmental variability is an important requisite to predict the severity of bleaching events.

The symbiosis of tropical corals with unicellular dinoflagellates is very sensitive to thermal stress. Even slightly enhanced temperatures can disrupt the tight association and lead to the expulsion of the zooxanthellae. The Andaman Sea coral reefs experienced an especially extensive bleaching event in 2010. Temperature exceeded the bleaching threshold of 30.1 °C by the end of March with peak values around 32 °C by the end of May extending down to 30 m depth. The temperature anomaly caused a complete whitening and high mortality in many of the reefs. However, we found spatial differences in bleaching and recovery related to frequent aperiodic upwelling of cold deep waters entrained by large amplitude internal waves (solitons) likely alleviating the heat stress for the corals. Here, we present data on coral tissue parameters of the massive coral Porites lutea collected along the soliton-exposed west and sheltered east sides of the Similan Islands, Andaman Sea, during samplings prior to, during and after the thermal anomaly, and relate bleaching onset to recovery to concomitant temperature recordings indicating soliton impact. Our data indicate that soliton-exposed corals are likely to be more resilient to bleaching than corals from sheltered areas, and indicate soliton-exposed reefs as potential refuges for corals from mass bleaching.

In oligotrophic tropical coral reef environments tightly coupled benthic-pelagic material fluxes represent key biogeochemical processes sustaining high benthic productivity and overall ecosystem functioning. Tropical storms can severely impact the physico-chemical state of marine coastal ecosystems and are predicted to increase in intensity on global scale. Although tropical storms cause large-scale habitat devastation, there is only little information regarding their influence on ecosystem metabolism and benthic-pelagic coupling in coastal coral reef environments. Thus, this study investigates these processes in a typical Caribbean shallow water reef lagoon close to Puerto Morelos (Mexico) over the course of the tropical storm “Dolly” (2008). Pelagic and benthic lagoon metabolism were assessed by measuring oxygen fluxes along with dissolved organic carbon (DOC), particulate organic matter and chlorophyll a concentrations in lagoon waters. Our findings characterize the pelagic lagoon compartment as an overall heterotrophic environment, while the benthic community was generally net autotrophic. Tropical storm impact was clearly detectable by change in monitored lagoon water parameters and a significantly influence on pelagic and benthic lagoon metabolism, which responded rapidly (within 1-2 d) to storm-induced environmental change by increased pelagic and lowered benthic net primary production. Pelagic respiration was significantly increased (up to 11 d) following the later development of a phytoplankton bloom and concomitantly elevated DOC concentrations, while benthic respiration remained below pre-storm levels up to the end of the study period. These findings emphasize compartment-specific and rapid responses by reef lagoon communities with implications for the functioning of benthic-pelagic coupling affected by tropical storm disturbances.

Cold water corals (CWC) are commonly known as slow growing organisms compared to their tropical congeners. This may be attributed to the low temperature they thrive in or to their lack of autotrophic symbionts. However, recent sighting of deep-sea corals, e.g. Lophelia pertusa growing on oil rigs, exhibit high growth rates. The measured growth rate naturally varies on the measure that is applied, for instance length extension versus CaCO3 precipitation. Skeletal characteristics may be different between species, for example some corals like Desmophyllum dianthus grow dense skeletons with pronounced growth in girth. Additionally few growth rates of CWC have been measured in situ and therefore true growth performance may be underestimated. Commonly growth is indirectly measured via dating techniques, estimated or determined in vivo in the laboratory. Corals isolated from their natural habitat and consequently under very different conditions may not show realistic metabolic responses. Here we show results of a study on short-term growth of Desmophyllum dianthus in situ and in an on-site flow through system. Aquaria corals exhibited growth rates of only one third compared to specimens in the field. Accordingly CWC growth may be underestimated in their growth potential when only studied in the laboratory.

Ocean acidification (OA) caused by the anthropogenic induced climate change via increasing CO2 release may be one of the main threats to the marine realm. OA will be a challenge to most marine calcifiers, but cold water corals are thought to be particularly affected owing to the nature of their cold and often deep habitat. The ‘Fjordo Comau’ (Chilean Patagonia) already today exhibits pCO2 values that are predicted for the year 2100 in the IPCC scenarios, comprising pH gradients up to 0.6 within the first? 225 m. Nevertheless, the ubiquitous cold water coral Desmophyllum dianthus thrives apparently unimpaired along these gradients. It forms dense banks along the fjord and moreover occurs as a member of a deep water emergence community as shallow as 12 m. Herein we present results of an in situ experiment cross-transplanting corals between two sites with a pH difference of ~ 0.15 (pH of 7.93 ± 0.09 and 7.78 ± 0.11). Growth was measured with the buoyancy weight method and two weeks were sufficient to show clear weight increase, still rates were relatively variable (5.75 ± 3.26 [mg CaCO3 cm-2 d-1] and 0.29 ± 0.19 [% d-1]). No differences of short-term growth rates between the two sites could be detected. Either there are factors that outbalance the adverse effects of low pH and/or cold water corals in general or Desmophyllum dianthus in particular may have a great ability to acclimatize or even adapt to a broad range of environmental conditions including pH. Nevertheless there may be limiting boundaries that restrict distribution, especially in the future when pH values will further decline.

In Patagonia, Chile, an extensive Fjord system can be found. The Comau Fjord is located in the northern part and is characterized by steep walls, a high tidal range and is approximately 500 m deep. Along its course from mouth to head (horizontally, along isobaths) and with decreasing depth (vertically) it shows gradual changes in water parameters including pH and the associated carbonate chemistry. Desmophyllum dianthus is a cosmopolite coral usually found in deeper water (> 200 m). In the Comau Fjord it thrives in shallow depth up to 15 m and is distributed in a broad variety of water parameters, including a pH range of at least 0.5 units – likely more. This demonstrates the high adaptation ability of cold water corals to a relatively wide spectrum of pH values.

Coral reef ecosystems sustain their high productivity in an oligotrophic environment by the efficient recycling of nutrients and tight benthic-pelagic coupling. The basis for productivity within coral reefs is the primary production, which is accomplished by diverse benthic photosynthetic organisms and, to a minor contribution, by phytoplankton in the waters aloft. Photosynthesis is determined by the availability of light, influenced by water depth and turbidity, and the availability of inorganic nutrients, essential for the organic synthesis of vital substances like amino acids. Benthic photosynthesis in coral reefs is characterised by the high abundance of manifold zooxanthellae bearing hosts, in particular scleractinian corals. Findings of the following chapters are presented from the organism to the ecosystem level (chapter 1-5), concerning organic matter recycling (nutrient availability) and energy conversion (light availability and photosynthesis) within a coral reef ecosystem. Nutrient and light availability vary likewise between ecosystems and are comparatively investigated at the Similan Islands in the Andaman Sea of the Indian Ocean (chapter 6-8), concerning environmental conditions, benthic community composition, primary production and heterotrophy.

Coral reef ecosystems sustain their high productivity in an oligotrophic environment by the efficient recycling of nutrients and tight benthic-pelagic coupling. The basis for productivity within coral reefs is the primary production, which is accomplished by diverse benthic photosynthetic organisms and, to a minor contribution, by phytoplankton in the waters aloft. Photosynthesis is determined by the availability of light, influenced by water depth and turbidity, and the availability of inorganic nutrients, essential for the organic synthesis of vital substances like amino acids. Benthic photosynthesis in coral reefs is characterised by the high abundance of manifold zooxanthellae bearing hosts, in particular scleractinian corals. Findings of the following chapters are presented from the organism to the ecosystem level (chapter 1-5), concerning organic matter recycling (nutrient availability) and energy conversion (light availability and photosynthesis) within a coral reef ecosystem. Nutrient and light availability vary likewise between ecosystems and are comparatively investigated at the Similan Islands in the Andaman Sea of the Indian Ocean (chapter 6-8), concerning environmental conditions, benthic community composition, primary production and heterotrophy.

Coral reef ecosystems sustain their high productivity in an oligotrophic environment by the efficient recycling of nutrients and tight benthic-pelagic coupling. The basis for productivity within coral reefs is the primary production, which is accomplished by diverse benthic photosynthetic organisms and, to a minor contribution, by phytoplankton in the waters aloft. Photosynthesis is determined by the availability of light, influenced by water depth and turbidity, and the availability of inorganic nutrients, essential for the organic synthesis of vital substances like amino acids. Benthic photosynthesis in coral reefs is characterised by the high abundance of manifold zooxanthellae bearing hosts, in particular scleractinian corals. Findings of the following chapters are presented from the organism to the ecosystem level (chapter 1-5), concerning organic matter recycling (nutrient availability) and energy conversion (light availability and photosynthesis) within a coral reef ecosystem. Nutrient and light availability vary likewise between ecosystems and are comparatively investigated at the Similan Islands in the Andaman Sea of the Indian Ocean (chapter 6-8), concerning environmental conditions, benthic community composition, primary production and heterotrophy.