Beschreibung: Background: The widespread Indo-Pacific coral species Pocillopora acuta Lamarck, 1816 displays varying levels of asexual versus sexual reproduction, with strong repercussions on genetic diversity, connectivity and genetic structuring within and among populations. For many geographic regions, baseline information on genetic diversity is still lacking, particularly in the Andaman Sea. The region suffered a massive heat-induced bleaching event in 2010 with high coral cover loss of branching coral species such as P. acuta. A subsequent bleaching in 2016, however, revealed a mild bleaching response in pocilloporids compared to other coral taxa in the region, suggesting that rare, heat tolerant genotypes had been selected by the 2010 bleaching event. In order to test whether this potential ‘evolutionary rescue’ event has led to a low genetic diversity, we conducted a population genetic survey covering a total of nine different P. acuta populations (336 individuals) along a 50 km coastal stretch around Phuket Island, Thailand. We used six microsatellite markers to assess genotypic diversity and to determine the prevalent mode of reproduction (i.e. sexual or asexual recruitment). Results: In contrast to other Indian Ocean P. acuta populations, the majority of corals in this study adopted a sexual reproduction mode (75% across all populations). At the same time, substantial regional gene flow was observed around Phuket Island with strong genetic differentiation as indicated by three genetic clusters that were separated by only a few kilometers. Patterns of isolation by distance over 0.7 – 40 km suggest small-scale genetic barriers, such as changing currents throughout each monsoonal season, potentially contributing to locally restricted dispersal of P. acuta larvae. Conclusions: The occurrence of distinct genetic clusters within short coastal stretches suggests that the 2010 bleaching event has not led to extreme genetic impoverishment. While more in-depth genomic analyses are necessary to investigate changes in genetic diversity following extreme bleaching events, our results will help guide conservation efforts to maintain genetic diversity of a coral species that likely will be dominant in future, warmer Andaman Sea reefs.

Beschreibung: Pocillopora damicornis (Linnaeus, 1758), a species complex, consists of several genetic lineages, some of which likely represent reproductively isolated species, including the species Pocillopora acuta Lamarck, 1816. Pocillopora acuta can exhibit similar morphological characteristics as P. damicornis, thus making it difficult to identify species-level taxonomic units. To determine whether the P. damicornis-like colonies on the reefs in the Andaman Sea (previously often identified as P. damicornis) consist of different species, we sampled individual colonies at five sites along a 50 km coastal stretch at Phuket Island and four island sites towards Krabi Province, Thailand. We sequenced 210 coral samples for the mitochondrial open reading frame and identified six distinct haplotypes, all belonging to P. acuta according to the literature. Recently, P. acuta was observed to efficiently recolonize heat-damaged reefs in Thailand as well as globally, making it a potentially important coral species in future reefs. Specifically in the light of global change, this study underscores the importance of high-resolution molecular species recognition, since taxonomic units are important factors for population genetic studies, and the latter are crucial for management and conservation efforts.

Beschreibung: Laboratory experiments were conducted in the climate chambers at GEOMAR Helmholtz Centre for Ocean Research Kiel in the time between March and November 2018. Experiments were designed to study the effect of long-term (1 month) exposure to low salinity in osmoconforming invertebrates. The study organisms (Asterias rubens, Mytilus edulis, Littorina littorea, Diadumene lineata, Strongylocentrotus droebachiensis and Psammechinus milliaris) were collected in Kiel Fjord, Eckernförder Bight or the Kattegat from spring to autumn 2018. Organisms were acclimated to climate chamber conditions for 1 week (under habitat salinity, 14˚C, constant aeration) and then subjected to salinity acclimation for 1-2 weeks until the final salinity treatment level was reached. Then different salinity treatments were maintained for 4 weeks. Water physiochemistry (temperature, salinity, pH, nitrite, nitrate, phosphate) was recorded frequently. After the experiment, samples were taken from tissues to measure total osmolality (mosmol/kg) with an osmomat, and inorganic ions (mmol/kg or µmol/g wet mass). Anions were measured with a novel protocol via ion chromatography, cations were measured via flame photometry. Organic osmolytes were measured via 1H-NMR.

Beschreibung: Low-salinity stress can severely affect the fitness of marine organisms. As desalination has been predicted for many coastal areas with ongoing climate change, it is crucial to gain more insight in mechanisms that constrain salinity acclimation ability. Low-salinity induced depletion of the organic osmolyte pool has been suggested to set a critical boundary in osmoconforming marine invertebrates. Whether inorganic ions also play a persistent role during low-salinity acclimation processes is currently inconclusive. We investigated the salinity tolerance of six marine invertebrate species following a four-week acclimation period around their low-salinity tolerance threshold. The species investigated were Asterias rubens, Mytilus edulis, Littorina littorea, Diadumene lineata, Strongylocentrotus droebachiensis and Psammechinus milliaris. To obtain complete osmolyte budgets of seawater, body fluids and tissues we quantified total osmolality (via osmometer), organic osmolytes (methylamine and free amino acids) via 1H-NMR spectroscopy and inorganic osmolytes (anions and cations) via flame photometry and a novel protocol using ion-chromatography. We further determined the fitness proxies survival, growth and tissue water content. Our data show the importance of the organic and inorganic osmolyte pool during low-salinity acclimation. It also shows the importance of specific compounds in some species. This data can be used in future osmolyte and salinity tolerance research. This type of data is essential to establish reliable physiological limits of species in order to estimate consequences of future salinity changes with ongoing climate change. It can be used to assess the salinity tolerance capacity and to obtain a better understanding of the basic mechanisms that are utilized in a wide range of species. The established cellular inorganic and organic osmolyte profiles can build a foundation for applied cellular physiological research, for example for designing suitable buffers for in vitro assays as these buffers need to incorporate complex organic and inorganic osmolyte changes. Knowledge about cellular and whole-organism biochemistry and physiology is absolutely crucial for characterizing the functions of genes that are under selection by climate change stressors. A quantitative knowledge of cellular osmolyte systems is key to understand the evolution of euryhalinity and to characterize targets of selection during rapid adaptation to ongoing desalination.

Beschreibung: Laboratory experiments were conducted in the climate chambers at GEOMAR Helmholtz Centre for Ocean Research Kiel in the time between March and November 2018. Experiments were designed to study the effect of long-term (1 month) exposure to low salinity in osmoconforming invertebrates. The study organisms (Asterias rubens, Mytilus edulis, Littorina littorea, Diadumene lineata, Strongylocentrotus droebachiensis and Psammechinus milliaris) were collected in Kiel Fjord, Eckernförder Bight or the Kattegat from spring to autumn 2018. Organisms were acclimated to climate chamber conditions for 1 week (under habitat salinity, 14˚C, constant aeration) and then subjected to salinity acclimation for 1-2 weeks until the final salinity treatment level was reached. Then different salinity treatments were maintained for 4 weeks. Water physiochemistry (temperature, salinity, pH, nitrite, nitrate, phosphate) was recorded frequently. Throughout the experiment survival was recorded. Before and after the experiment organism weight and, where feasible, size was measured. Weight data was also used to calculate tissue water content. This dataset comprises the physiological fitness parameters for each species at the respective salinity treatment. Given are data for survival, growth and tissue water content.

Beschreibung: Climate change is predicted to alter salinity in many coastal regions. This exerts significant physiological stress on coastal invertebrates whose body fluid osmolality follows that of seawater ('osmoconformers'). Osmolytes are the cellular actors in osmoconformers that regulate acclimation to salinity changes. Inspite of their cellular importance in salinity tolerance, cellular volume regulation and its osmotic components, are not sufficiently understood. Which compounds are commonly used as osmolytes? Are inorganic and organic osmolytes used in long-term salinity acclimation? Are there taxonomic- or tissue specific differences? By conducting an extensive literature search, this study aimed to answer these questions. By using a meta-analysis approach over an ordinary literature review we were able to statistically evaluate the individual effect sizes by computing a summary effect for multiple studies to estimate the mean of the distribution of the true effect sizes. Meta-analysis is useful to reveal research gaps, common actors across taxa, or overall effects of biotic factors. We thus conducted a systematic review and meta-analysis of osmolyte data (both organic and inorganic) utilized by osmoconforming marine invertebrates during a 〉14-day acclimation to reduced salinity. This study offers a valuable overview of the various listed organic compounds across species and whether and in which organisms they are used as osmolytes under low salinity stress. This study thereby creates a valuable baseline for future research. 2389 studies were screened according to standard systematic review procedures (title scan, abstract scan and full-exam) resulting a total of 56 studies that fulfilled the search criteria. The data includes the list of all papers that underwent a full-exam in the systematic review process and passed the search criteria and study details of the studies used for meta-analysis. For all included studies the input data necessary to conduct a meta-analysis with a hedge's g effect size is given. Namely, mean osmolyte concentrations, variance measure and replicate numbers are given for the high and low salinity treatment. The data for any benthic osmoconforming species and any osmolyte type is included. The data table is sorted by study but gives additional information on taxonomy, experimental details, study design, osmolyte type, tissue type, etc. Additionally, data is available for a number of studies that reported an extensive osmolyte budget (i.e. multiple compounds). Here, for each study and study organism osmolytes (that were present in more than one study) are listed as percent of the total organic osmolyte pool. This dataset is the first systematically compiled list of studies investigating osmolyte concentrations in osmoconformers after long-term (〉14 days) acclimation to low salinity. Data can be used to compare own osmolyte data (species/osmolyte compound) with a comprehensive list of osmolyte literature data. Additionally, this data can be used to address other hypotheses via meta-analysis. As this was a systematic review, no biological samples were collected in this study. Information of the origin of the data from each of the included studies can be found in the list of all included studies.

Beschreibung: This table contains a list of studies that report concentrations for multiple organic osmolytes. These concentrations were calculated into proportions of the total organic osmolyte pool and grouped by taxa (shown in figure 8 of Podbielski et al. 2022). If the sum deviates from 100% this may be caused by using the values for total solute given in the respective papers whenever they were reported. Here, slight deviations from 100% maybe due to rounding errors. Larger deviations are likely caused when total solutes and specific osmolytes were quantified with different techniques. For example, total solutes are sometimes determined as Ninhydrine-positive substances or quaternary ammonium compounds. This may include methylamines or other free amino acids which are not determined via targeted techniques to measure amino acids (i.e. via amino acid analyser). The column "Osmolyte, other" combines values for compounds (〈5%) and, if present, values for other compounds, which were data given by the respective papers.

Beschreibung: All studies included in the meta-analysis are listed with study details such as experimental design, species studied, number of replicates, salinity levels and mean values and variances of the studied parameters. Data are only reported if full data (replication, mean, variation) were given.

Beschreibung: Laboratory experiments were conducted in the climate chambers at GEOMAR Helmholtz Centre for Ocean Research Kiel in the time between March and November 2018. Experiments were designed to study the effect of long-term (1 month) exposure to low salinity in osmoconforming invertebrates. The study organisms (Asterias rubens, Mytilus edulis, Littorina littorea, Diadumene lineata, Strongylocentrotus droebachiensis and Psammechinus milliaris) were collected in Kiel Fjord, Eckernförder Bight or the Kattegat from spring to autumn 2018. Organisms were acclimated to climate chamber conditions for 1 week (under habitat salinity, 14˚C, constant aeration) and then subjected to salinity acclimation for 1-2 weeks until the final salinity treatment level was reached. Then different salinity treatments were maintained for 4 weeks. Water physiochemistry (temperature, salinity, pH, nitrite, nitrate, phosphate) was recorded frequently. After the experiment, samples were taken from seawater and body fluids to measure total osmolality (mosmol/kg) with an osmomat and inorganic ions (mmol/l). No body fluid samples were taken from Diadumene lineata as organisms were too small and volumes too low. Anions were measured with a novel protocol via ion chromatography, cations were measured via flame photometry.

Beschreibung: From January 2020 to January 2022, temperature, salinity, and oxygen (only July 2020 - April 2021) data were logged with an AANDERAA oxygen sensor 3835 and a SEABIRD SBE 37-SI MicroCAT CT(D) in 10-minutes intervals at GEOMAR (Kiel, Germany) pier at 54°19'48.8N 10°08'59.6E. The sensor system is mounted to a floating platform such that a continuous depth of 1 m is ensured at any time. Oxygen data were corrected for salinity, temperature and depth following the manual for Aanderaa Optodes using the salinity and temperature measurements from the SEABIRD SBE 37-SI MicroCAT CT(D) sensor. After cleaning and other re-boots of the sensor package, temperature, salinity and oxygen data tend to deviate from true values. Hence, 60 minutes of data after any re-boot (after sensor servicing with re-deployment, data download or power failure) were deleted. Two major data gaps (January 2020 – July 2020, April 2021 – June 2021) are due to longer periods when the sensors were serviced in the workshop.