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1. Environmental Controls on the Distribution of Modern Benthic Foraminifera in the Florida Everglades and Their Use as Paleoenvironmental Indicators

   https://doi.org/10.2113/gsjfr.51.3.182  

   Verlaak, Zoë R.; Collins, Laurel S. (July 2021, Journal of Foraminiferal Research)

   null (Ed.)

   ABSTRACT This study examined the environmental factors that control the distribution of modern foraminiferal assemblages in the Everglades in order to provide baseline data for a paleoenvironmental study. Total assemblages from the surface 2 cm of 30 sites across the marsh and mangrove environments of southwest Florida were investigated. Eight environmental variables, including average salinity, salinity range, pH, total phosphorus, temperature, and dissolved oxygen, and total organic carbon and total inorganic carbon measured on bulk sediments, as well as the elevation and distance from the coastline were determined for each of the 30 sampling locations. In total, 82 species were identified, the majority of which were calcareous. Diversity decreases, dominance increases, and agglutinated taxa increase from the coastline inland. Rotaliina are equally abundant across the intertidal environment, whereas Miliolina are common near the coast and in lagoons or inland lakes. The most important factor controlling foraminiferal distribution is total organic carbon, followed by total inorganic carbon, distance from coastline, total phosphorus, and salinity. Jadammina macrescens and Miliammina fusca indicate lower salinities (<15 psu). Good indicators for higher salinities are Haplophragmoides wilberti (10–20 psu) and Arenoparrella mexicana (10–20 psu and 28–30 psu). Ammonia spp. prefer salinities >15 psu and Elphidium spp. >20 psu. Ammonia tepida, Helenina anderseni, Trochammina inflata, and A. mexicana prefer organic-rich sediments. Thus, the benthic foraminifera from Everglades sediments are excellent salinity proxies and can be used to determine the history of habitat change in this area as well as to assess past trends in the rate of sea level rise. 

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2. Synergistic Effects of Temperature and Salinity on the Gene Expression and Physiology of Crassostrea virginica

   https://doi.org/10.1093/icb/icz035  

   Jones, H. R.; Johnson, K. M.; Kelly, M. W. (May 2019, Integrative and Comparative Biology)

   Abstract The eastern oyster, Crassostrea virginica, forms reefs that provide critical services to the surrounding ecosystem. These reefs are at risk from climate change, in part because altered rainfall patterns may amplify local fluctuations in salinity, impacting oyster recruitment, survival, and growth. As in other marine organisms, warming water temperatures might interact with these changes in salinity to synergistically influence oyster physiology. In this study, we used comparative transcriptomics, measurements of physiology, and a field assessment to investigate what phenotypic changes C. virginica uses to cope with combined temperature and salinity stress in the Gulf of Mexico. Oysters from a historically low salinity site (Sister Lake, LA) were exposed to fully crossed temperature (20°C and 30°C) and salinity (25, 15, and 7 PSU) treatments. Using comparative transcriptomics on oyster gill tissue, we identified a greater number of genes that were differentially expressed (DE) in response to low salinity at warmer temperatures. Functional enrichment analysis showed low overlap between genes DE in response to thermal stress compared with hypoosmotic stress and identified enrichment for gene ontologies associated with cell adhesion, transmembrane transport, and microtubule-based process. Experiments also showed that oysters changed their physiology at elevated temperatures and lowered salinity, with significantly increased respiration rates between 20°C and 30°C. However, despite the higher energetic demands, oysters did not increase their feeding rate. To investigate transcriptional differences between populations in situ, we collected gill tissue from three locations and two time points across the Louisiana Gulf coast and used quantitative PCR to measure the expression levels of seven target genes. We found an upregulation of genes that function in osmolyte transport, oxidative stress mediation, apoptosis, and protein synthesis at our low salinity site and sampling time point. In summary, oysters altered their phenotype more in response to low salinity at higher temperatures as evidenced by a higher number of DE genes during laboratory exposure, increased respiration (higher energetic demands), and in situ differential expression by season and location. These synergistic effects of hypoosmotic stress and increased temperature suggest that climate change will exacerbate the negative effects of low salinity exposure on eastern oysters. 

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3. Impact of Reactive Oxygen Species Scavenging on the Intermediate Production of Anthracene and Anthraquinone in Fresh versus Saltwater Environments

   https://doi.org/10.1002/etc.5687  

   St_Romain, Scott_J; Basirico, Laura_M; Kim, Yong-Ha; Nolan, Emily_Vebrosky; Xu, Wei; Armbrust, Kevin_L (June 2023, Environmental Toxicology and Chemistry)

   Abstract While salinity can alter the photodegradation of hydrophobic organic compounds (HOCs), the cause of their altered kinetics in seawater is not well understood. Because HOC intermediate photoproducts are often more toxic than their parent compounds, characterizing the generation of intermediates in saline environments is needed to accurately predict their health effects. The present study investigated the influence of salinity on the generation of anthraquinone through the photolysis of anthracene and the generation of anthrone and 1-hydroxyanthraquinone from the photolysis of anthraquinone as well as their reactivities with hydroxyl radicals. This was conducted by measuring the photolysis rates of anthracene and anthraquinone and characterizing their product formation in buffered deionized water, artificial seawater, individual seawater halides (bromide, chloride, and iodide), dimethyl sulfoxide, furfuryl alcohol, and solutions of hydrogen peroxide. Salinity enhanced the persistence of anthraquinone by a factor >10 and altered its product formation, including the generation of the suspected carcinogen 1-hydroxyanthraquinone. In part, this was attributed to reactive oxygen species (ROS) scavenging by the seawater constituents chloride and bromide. In addition, anthraquinone and its hydroxylated products were found to be moderately to highly reactive with hydroxyl radicals, further illustrating their tendency to react with ROS in aqueous environments. The present study emphasizes the importance of considering the effects of salinity on organic contaminant degradation; it can significantly enhance the persistence of HOCs and alter their intermediate formation, subsequently impacting chemical exposure times and potential toxic effects on estuarine/marine organisms. Environ Toxicol Chem 2023;42:1721–1729. © 2023 SETAC. 

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4. Changes in Larval Oyster Swimming Behavior with Salinity and Larval Age

   https://doi.org/10.1086/725418  

   Manuel, Emily C.; Caracappa, Joseph; Munroe, Daphne (April 2023, The Biological Bulletin)

   Eastern oysters (Crassostrea virginica) are sessile, relying on a larval phase to disperse in estuaries. Oyster larval swimming behavior can alter dispersal trajectories and patterns of population connectivity. Experiments were conducted to test how both (1) acclimation time to new environmental conditions and (2) larval swimming behavior change with salinity and larval age. Acclimation time to changes in salinity was longest in lower salinity (6 ppt) and decreased with age. To test changes in behavior with salinity, larvae were placed into four salinities (6, 10, 16, and 22 ppt) where swimming was recorded. To test changes in behavior with age, larvae aged 6, 12, and 15 days were recorded. In both experiments, swimming paths were mapped in two dimensions, behavior of each path was categorized, and speed, direction, and acceleration were calculated. The frequency of upward, neutral, and downward swimming behaviors did not differ across salinity treatments but did vary with age, whereas the frequency of behavior types varied with both salinity and ontogeny. As an example, diving was observed more frequently in low salinity, and more downward helices were observed in moderate salinity, while younger larvae swam upward with more frequency than older larvae. Surprisingly, diving was observed in 10%–15% of all larvae across all ages. Given the consequence of larval behavior to marine invertebrate dispersal, changes in swimming over larval age and in response to environmental changes have important implications to marine population stability and structure. 

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5. Natural and synthetic microfibers alter growth and behavior in early life stages of estuarine organisms

   https://doi.org/10.3389/fmars.2022.991650  

   Siddiqui, S.; Hutton, S. J.; Dickens, J. M.; Pedersen, E. I.; Harper, S. L.; Brander, S. M. (January 2023, Frontiers in Marine Science)

   Increasing shares of microfibers are being detected in environmental samples and a closer look to identify the risk associated with them using ecologically relevant endpoints, especially at sensitive early life stages, is needed. To assess exposure hazards, we used rope samples representative of fiber types ubiquitous in coastal systems, where microfibers are often the most common debris type found in the water column. To compare responses to natural vs. synthetic microfibers, we used rinsed “natural” cotton, polyester, and polypropylene microfibers (80-150 µm length, 8-20 µm width) created from the rope. Larval and juvenile estuarine indicator species Inland Silverside (Menidia beryllina) and mysid shrimp (Americamysis bahia) , respectively, were exposed to these three microfiber types at three concentrations (3, 10, 30 particles/ml) along a 5-25 PSU salinity gradient to mimic estuarine conditions. Behavioral responses, growth, and ingestion were measured. The cotton microfibers were not detected in the digestive tracts of Silversides, however, both the polyester and polypropylene microfibers were detected in the Silversides’ stomach and gut lining. None of the fiber types were detected in mysid shrimps. Mysids exposed to cotton microfibers had fewer behavioral effects compared to Silversides, who responded more to cotton. Cotton exerted no effect on growth in Silversides but did cause reduced growth in the mysids at the two lower salinities. In contrast, polyester and polypropylene were identified to have a significant dose dependent effect on mysid and Silverside behavior as well as growth was affected in at least one of the three salinities at concentrations as low as 3 particles/ml. Cotton impacted both the organism’s behavior more at higher salinities, whereas polyester and polypropylene had more impacts at lower salinities. This raises concerns for microfiber impacts on estuarine ecosystems and the need for policies to limit microfiber production and outfall into the aquatic environment. 

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