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AbstractOxygen bioavailability is declining in aquatic systems worldwide as a result of climate change and other anthropogenic stressors. For aquatic organisms, the consequences are poorly known but are likely to reflect both direct effects of declining oxygen bioavailability and interactions between oxygen and other stressors, including two-warming and acidification-that have received substantial attention in recent decades and that typically accompany oxygen changes. Drawing on the collected papers in this symposium volume ("An Oxygen Perspective on Climate Change"), we outline the causes and consequences of declining oxygen bioavailability. First, we discuss the scope of natural and predicted anthropogenic changes in aquatic oxygen levels. Although modern organisms are the result of long evolutionary histories during which they were exposed to natural oxygen regimes, anthropogenic change is now exposing them to more extreme conditions and novel combinations of low oxygen with other stressors. Second, we identify behavioral and physiological mechanisms that underlie the interactive effects of oxygen with other stressors, and we assess the range of potential organismal responses to oxygen limitation that occur across levels of biological organization and over multiple timescales. We argue that metabolism and energetics provide a powerful and unifying framework for understanding organism-oxygen interactions. Third, we conclude by outlining a set of approaches for maximizing the effectiveness of future work, including focusing on long-term experiments using biologically realistic variation in experimental factors and taking truly cross-disciplinary and integrative approaches to understanding and predicting future effects.

Land use and land cover (LULC) can significantly alter river water, which can in turn have important impacts on downstream coastal ecosystems by delivering nutrients that promote marine eutrophication and hypoxia. Well-documented in temperate systems, less is known about the way land cover relates to water quality in low-lying coastal zones in the tropics. Here we evaluate the catchment LULC and the physical and chemical characteristics of six rivers that contribute flow into a seasonally hypoxic tropical bay in Bocas del Toro, Panama. From July 2019 to March 2020, we routinely surveyed eight physical and chemical characteristics (temperature, specific conductivity, salinity, pH, dissolved oxygen (DO), nitrate and nitrite, ammonium, and phosphate). Our goals were to determine how these physical and chemical characteristics of the rivers reflect the LULC, to compare the water quality of the focal rivers to rivers across Panama, and to discuss the potential impacts of river discharge in the Bay. Overall, we found that the six focal rivers have significantly different river water characteristics that can be linked to catchment LULC and that water quality of rivers 10 s of kilometers apart could differ drastically. Two focal catchments dominated by pristine peat swamp vegetation in San San Pond Sak, showed characteristics typical of blackwater rivers, with low pH, dissolved oxygen, and nutrients. The remaining four catchments were largely mountainous with >50% forest cover. In these rivers, variation in nutrient concentrations were associated with percent urbanization. Comparisons across Panamanian rivers covered in a national survey to our focal rivers shows that saltwater intrusions and low DO of coastal swamp rivers may result in their classification by a standardized water quality index as having slightly contaminated water quality, despite this being their natural state. Examination of deforestation over the last 20 years, show that changes were

Broadly distributed species need to perform well in a range of environmental conditions, but knowledge of how wide‐ranging marine larvae perform along latitudinal gradients remains limited. The fatty acid composition of larvae is important for their physiological responses to changing conditions. Here, we investigated the fatty acid composition of the last, non‐feeding stage of barnacle larvae (cyprids) using an integrative (larvae–environment) and comparative (latitudinal) approach. We measured fatty acids in the pelagic particulate matter and cyprids from Chthamalus bisinuatus, Chthamalus proteus, and Semibalanus balanoides from tropical to polar (Arctic) latitudes to identify potential food sources during the feeding larval stages (nauplius) that precede the cyprids and to ascertain larval capacity to integrate neutral (energetic) and polar (structural) fatty acids. We demonstrate that particulate matter in tropical waters mainly consisted of low‐quality saturated fatty acids derived from detrital pathways, while particulate matter from polar waters was rich in polyunsaturated fatty acids originating from living microalgae. Across the studied regions, neutral fatty acids were assimilated from various food sources including diatoms, dinoflagellates, detritus, and microeukaryotes. Cyprids consistently retained higher essential fatty acid levels than the relative share in the particulate matter. Particularly, the essential docosahexaenoic acid (22:6ω3), which was scarce in the particulate matter, was highly retained across all species but highest for the tropical cyprids. We argue that this latitudinal pattern in fatty acid retention is related to periods of reduced nutrient intake, increased energetic and/or synthetic requirements, and responses to physical large‐scale differences in environmental conditions. [ABSTRACT FROM AUTHOR]

Ocean Sampling Day was initiated by the EU-funded Micro B3 (Marine Microbial Biodiversity, Bioinformatics, Biotechnology) project to obtain a snapshot of the marine microbial biodiversity and function of the world's oceans. It is a simultaneous global mega-sequencing campaign aiming to generate the largest standardized microbial data set in a single day. This will be achievable only through the coordinated efforts of an Ocean Sampling Day Consortium, supportive partnerships and networks between sites. This commentary outlines the establishment, function and aims of the Consortium and describes our vision for a sustainable study of marine microbial communities and their embedded functional traits.

The identity of wild cloning sea star larvae has been a mystery since they were first documented in the Caribbean. The most commonly collected cloning species was thought to belong to the Oreasteridae, on the basis of similarity with sequences from Oreaster reticulums and Oreaster clavatus. This larval form has recently been linked to a rare benthic juvenile. As part of two larger DNA barcoding projects, we collected cloning asteroid larvae from the Caribbean coast of Panama and compared them to a large reference database of tropical echinoderms. Morphological and DNA barcode data from the cytochrome c oxidase subunit I gene demonstrated that Panamanian larvae belonged to the same operational taxonomic unit as those recovered in previous studies of cloning larvae from the Caribbean. Much to our surprise, sequences from these larvae clearly identified them as belonging to Valvaster striatus, a species typically considered to be endemic to the Indo-West Pacific. A lineage of Mithrodia clavigera that occurs in both the Caribbean and the Indo-West Pacific also has cloning larvae, suggesting that this unusual life history has allowed larvae to pass around the Cape of Good Hope and the Benguela upwelling region, which is a barrier to dispersal for most tropical marine invertebrates., Introduction Cloning can be induced in larvae of numerous echinoderm species under laboratory conditions; however, natural asexual reproduction of larvae in the wild has been reported for only a few [...]

In species with complex life cycles, early developmental stages are often less thermally tolerant than adults, suggesting that they are key to predicting organismal response to environmental warming. Here we document the optimal and lethal temperatures of larval sea urchins, and we use those to calculate the warming tolerance and the thermal safety margin of early larval stages of seven tropical species. Larvae of Echinometra viridis, Echinometra lucunter, Lytechinus williamsi, Eucidaris tribuloides, Tripneustes ventricosus, Clypeaster rosaceus, and Clypeaster subdepressus were reared at 26, 28, 30, 32, and 34 [degrees]C for 6 days. The temperatures at which statistically significant reductions in larval performance are evident are generally the same temperatures at which statistically significant reductions in larval survival were detected, showing that the optimal temperature is very close to the lethal temperature. The two Echinometra species had significantly higher thermal tolerance than the other species, with some surviving culture temperatures of 34 [degrees]C and showing minimal impacts on growth and survival at 32 [degrees]C. In the other species, larval growth and survival were depressed at and above 30 or 32 [degrees]C. Overall, these larvae have lower warming tolerances (1 to 5 [degrees]C) and smaller thermal safety margins (-3 to 3 [degrees]C) than adults. Survival differences among treatments were evident by the first sampling on day 2, and survival at the highest temperatures increased when embryos were exposed to warming after spending the first 24 hours at ambient temperature. This suggests that the first days of development are more sensitive to thermal stress than are later larval stages., Introduction Environmental warming is one of the greatest current threats to biodiversity. Many studies of thermal limits and thermal performance curves have been conducted on adult ectotherms (Nguyen et al., [...]

Abstract. Chemical signaling, especially signaling with waterborne cues, is an important mode of communication between conspecifics of aquatic organisms. Although conspecific associations play an important role in sex allocation of [...]

Previous research focusing on pelagic gastropods in the open ocean has demonstrated that many morphospecies comprise multiple distinct clades or cryptic species that can be distinguished with DNA sequence data. To date, the genetic diversity of the pelagic gastropod fauna of the tropical East Pacific, especially in shallow coastal waters, remains largely unexplored. To document the diversity of pterotracheoids (formerly heteropods) from the coastal waters of the Bay of Panama, we collected, photographed and sequenced fragments of mitochondrial cytochrome c oxidase subunit I (COI) and 16S ribosomal DNA for 60 atlantids, 3 carinariids and 6 pterotracheids. In addition to the COI barcode, our results include the first published 16S sequences for these groups. We found 11 operational taxonomic units (OTUs): 9 in the genus Atlanta, 1 Carinaria and 1 Firoloida. We report the presence of Atlanta oligogyra (Clades A and B), Atlanta turriculata, Atlanta lesueurii, Atlanta helicinoidea (Clade B), Atlanta plana, Atlanta echinogyra, Atlanta inflata and Atlanta frontieri through comparisons of our sequences with previously published sequences. We did not find Atlanta gaudichaudi, Atlanta inclinata, Atlanta tokiokai, Atlanta gibbosa, Atlanta peronii, or Oxygyrus inflatus, which have previously been reported from the region. Haplotype networks and estimates of ΦST illustrate how some species show population differentiation across the tropical Indo‐Pacific region, whereas others show little apparent population structure. For example, the most common haplotypes of A. inflata and of A. turriculata occur in the Indian Ocean, the Central and West Pacific and the tropical East Pacific, whereas individuals of A. frontieri from the Indian Ocean do not share haplotypes with individuals of A. frontieri from the Pacific Ocean. Analyses were limited by sample sizes, but these data suggest that population genetics approaches may be useful for reconstructing population histories of these important, but overlooked, components of the plankton. [ABSTRACT FROM AUTHOR]

. A modification of a semi-quantitative colorbased enzyme assay was used to quantify the activity of 19 enzymes (5 peptidases, 3 lipases, 3 phosphotases, and 8 carbohydrases) during five stages of development in eight species of calyptraeid gastropods. Sixteen of the 19 enzymes showed a significant effect of mode of development on the concentration of the reaction product after incubation of homogenates standardized for protein content. The overall pattern was that planktotrophs showed the highest activities, followed by adelphophages, and nonfeeding embryos, which had the lowest enzyme activities. Thirteen enzymes showed significant differences across developmental stages. Of these, eight showed a clear increase during development. Only one of the enzymes showed a sudden jump in activity between the unfed, pre-hatching stage and post-hatching stages that were fed Isochrysis galbana. In three cases, ANOVA identified two exclusive, significantly different groups of species. In naphthol-AS-BI-phosphohydrolase, the measured absorbance of Crucibulum spinosum samples was significantly higher than in all of the other species. The activity of α-fucosidase in Crepipatella occulta was significantly greater than in the other seven species. Finally, the activity of β-galactosidase was significantly higher in occulta. Crucibulum spinosum, and Bostrycapulus calyptraeformis than in the four Crepidula species. This is the only enzyme for which there is an indication of a phylogenetic effect. Relative enzyme activities were similar to those reported for other herbivorous gastropods, with the three phosphohydrolases, four carbohydrases (β-galactosidase, β-glucuronidase, N-acetyl-β-glucosaminidase, and α-fucosidase), and leucine arylamidase showing high activities., Introduction From the perspective of energetics, marine invertebrates can be roughly divided into those that have feeding, planktonic larvae (planktotrophic development) and those that do not (referred to here as [...]

Adelphophagic development, where embryos consume sibling embryos or nurse eggs, is particularly common in marine caenogastropods and some families of polychaetes. When exogenous nutrition is provided before hatching, egg size and hatching size can be uncoupled, but advantages and constraints of adelphophagic development compared to development from large eggs are unknown. Here we examine temperature-mediated plasticity in offspring size, brooding duration, and fecundity in the adelphophagic marine gastropod Crepidula cf. onyx. We use these data combined with previously published data on two planktotrophic Crepidula and two Crepidula species that develop from large eggs to test hypotheses about the consequences of adelphophagic development and patterns of variation in offspring size. In Crepidula cf. onyx, egg size shows no significant effect of temperature. Hatching size is significantly larger at 28 °C than at 23 °C but proceeds from fewer eggs per capsule at 28 °C. Hatching size is therefore decoupled from both egg size and the number of eggs per capsule. Although development is faster at the higher temperature, broods are produced roughly every 26-27 days at both temperatures. Increased rate of development has been cited as a potential advantage of adelphophagic development in muricids, but the adelphophagic C. cf. onyx did not develop more quickly than C. atrasolea or C. ustulatulina, species that produce similarly sized hatchlings from large eggs. Comparisons across calyptraeid species support the role of adelphophagy in increasing variance in offspring size. This increased variability is primarily expressed within broods or among broods from the same female, not among females., Introduction Marine invertebrates have evolved a number of ways for small eggs packaged by mothers into gelatinous egg masses or capsules to develop into large hatchlings. For example, in volutid [...]