High Levels of Sediment Contamination Have Little Influence on Estuarine Beach Fish Communities

While contaminants are predicted to have measurable impacts on fish assemblages, studies have rarely assessed this potential in the context of natural variability in physico-chemical conditions within and between estuaries. We investigated links between the distribution of sediment contamination (metals and PAHs), physico-chemical variables (pH, salinity, temperature, turbidity) and beach fish assemblages in estuarine environments. Fish communities were sampled using a beach seine within the inner and outer zones of six estuaries that were either heavily modified or relatively unmodified by urbanization and industrial activity. All sampling was replicated over two years with two periods sampled each year. Shannon diversity, biomass and abundance were all significantly higher in the inner zone of estuaries while fish were larger on average in the outer zone. Strong differences in community composition were also detected between the inner and outer zones. Few differences were detected between fish assemblages in heavily modified versus relatively unmodified estuaries despite high concentrations of sediment contaminants in the inner zones of modified estuaries that exceeded recognized sediment quality guidelines. Trends in species distributions, community composition, abundance, Shannon diversity, and average fish weight were strongly correlated to physico-chemical variables and showed a weaker relationship to sediment metal contamination. Sediment PAH concentrations were not significantly related to the fish assemblage. These findings suggest that variation in some physico-chemical factors (salinity, temperature, pH) or variables that co-vary with these factors (e.g., wave activity or grain size) have a much greater influence on this fish assemblage than anthropogenic stressors such as contamination

Feeding performance of juvenile hatchery-reared spotted seatrout Cynoscion nebulosus

The feeding performance of individual hatchery-reared (HR) and wild juvenile spotted seatrout Cynoscion nebulosus was compared across a series of six 1·5 h feeding exposures over a 3 day period in a controlled experiment. The predation cycle served as a context for discerning feeding performance elements. The experimental design facilitated assessments of the effects of experience, motivation due to hunger or satiation and prey density and encounter frequency. Although feeding success improved significantly across successive trials for both groups of C. nebulosus, wild C. nebulosus successfully captured and consumed significantly more Palaemonetes spp. prey and completed most performance metrics more efficiently than HR C. nebulosus. Total exposure time decreased with experience for both groups of C. nebulosus; however, HR C. nebulosus took longer to complete feeding exposures. Underpinning this difference was the time spent by HR C. nebulosus in non-search mode and for completing various foraging behaviours. Nevertheless, juvenile HR C. nebulosus exhibited sufficient foraging plasticity to switch from a pelleted diet to live novel prey

Volcanic related methylmercury poisoning as the possible driver of the end-Devonian Mass Extinction

The end-Devonian global Hangenberg event (359 Ma) is among the most devastating mass extinction events in Earth\u2019s history, albeit not one of the \u201cBig Five\u201d. This extinction is linked to worldwide anoxia caused by global climatic changes. These changes could have been driven by astronomical forcing and volcanic cataclysm, but ultimate causes of the extinction still remain unclear. Here we report anomalously high mercury (Hg) concentration in marine deposits encompassing the Hangenberg event from Italy and Austria (Carnic Alps). The Hangenberg event recorded in the sections investigated can be here interpreted as caused by extensive volcanic activity of large igneous provinces (LIPs), arc volcanism and/or hydrothermal activity. Our results (very large Hg anomalies) imply volcanism as a most possible cause of the Hangenberg event, similar to other first order mass extinctions during the Phanerozoic. For the first time we show that apart from anoxia, proximate kill mechanism of aquatic life during the event could have been methylmercury formed by biomethylation of a volcanically derived, huge concentration of inorganic Hg supplied to the ocean. Methylmercury as a much more toxic Hg form, potentially could have had a devastating impact on end-Devonian biodiversity, causing the extinction of many pelagic species

Hypoxia Interrupts the Secondary Production Service Provided by Oyster Reef Macrofauna In Mississippi Sound, USA

Production by macrofauna associated with oyster reefs offers a multi-purpose indicator of ecosystem function, ecological integrity, and restoration success. We examined responses by oyster-reef-associated macrofauna to a hypoxic event across three subtidal oyster-reef complexes in western Mississippi Sound as part of a large-scale restoration program. Four hypotheses within the context of a Linear mixed model examined differences in the following: (1) the macrofauna relative to the hypoxic event; (2) subregions relative to the severity of hypoxia; (3) responses by key macrofaunal taxa; and (4) short-term macrofaunal recovery. Densities and production potential of the entire oyster-reef macrofaunal community as well as for six key taxa all abruptly decreased in connection with the hypoxic event. Overall, total production potential and total density were four-fold lower in the summer of 2015 during the hypoxic event than in the summer of 2014. The degree of macrofaunal impact corresponded with the severity of hypoxia on the landscape scale. Total density and total production averaged nearly three-fold lower and more than eight-fold lower respectively across two critically hypoxic reef complexes compared to the least affected reef complex. Taxon-specific responses depended on tolerances to hypoxia as well as modes of reproduction and dispersal. Short-term macrofaunal recovery indicated surprising ecological resilience relative to the hypoxic interruption. Detrimental macrofaunal effects ameliorated substantially within several months when total production potential was comparable to that of the previous year. However, the short-term recovery of key taxa varied with respect to the hypoxic event. Hypoxia-induced seasonal directionality reversed between summer 2015 and fall 2015, as evidenced by lower values for total density, total production, and the density and production of the larger-bodied crustaceans, Eurypanopeus and Palaemonetes. Secondary production offers a key functional indicator of multiple ecosystem services and an informative gauge of ecological disturbance. Associated macrofauna should be used more widely to assess the ecological function and recovery of oyster reefs. This study expands our understanding of a productive oyster reef ecosystem that is threatened by multiple environmental challenges

Large environmental disturbances caused by magmatic activity during the Late Devonian Hangenberg Crisis

A wide range of various proxies (e.g., mineralogy, organic carbon, inorganic geochemistry, C and Mo isotopes, and framboidal pyrite) were applied for interpretation of changing oceanic redox conditions, bioproductivity, and the regional history of magmatic activity. This resulted in internally consistent interpretation of the late Famennian Hangenberg Crisis in subtropical deepest water sites of the epeiric Rhenohercynian and Saxo\u2013Thuringian basins, as well as more open sites of the Paleo-Tethys Ocean. High mercury concentrations were detected in all of the studied sections, with the highest values strata in the Carnic Alps (up to 20 ppm) and Thuringia (up to 1.5 ppm). The beginning of the Hg anomaly and the presence of pyroclastic material, indicate that local magmatic activity was initiated before the deposition of the Hangenberg Black Shale (HBS). The onset of the HBS deposition coincided with the expansion of phosphate-enriched, anoxic to euxinic waters during short-lived CO2-greenhouse spike of a warm\u2013humid climate. Intensive magmatic activity was a trigger for climatic changes, an excessive eutrophication, and an accelerated burial of organic carbon during the Hangenberg transgressive pulse. The injection of catastrophic amounts of CO2, toxic elements and acids from volcanic activity could have led to acidification, mutation of spores, and episodes of mass mortality of marine plankton

Establishing Nearshore Marine Injuries for the Deepwater Horizon Natural Resource Damage Assesment Using AQUATOX

The Oil Pollution Act of 1990 (OPA) requires that the responsible party make the public whole for natural resource injuries attributable to an oil spill incident. We have presented our approach at establishing natural resource baseline conditions for multiple habitats in Coastal Mississippi and Alabama. This paper presents the subsequent steps that were taken to estimate natural resource injuries for the Deepwater Horizon Oil release (DWH) using AQUATOX Release 3.1 NME (Nearshore Marine Environments). TPAH (Total polycyclic aromatic hydrocarbon) exposure matrices in water and sediment were estimated over a spatial gradient based on observed data in Mississippi and Alabama. Bioaccumulation parameters were derived from literature and reasonable bioaccumulation calibration was verified using site specific data when available. TPAH was segregated into six different analyte groups, binned by Kow, based on observed sediment data. Toxicity data from NOAA and literature were used to estimate effects of TPAH and individual analytes on species observed on site. Combining each of these analyses, total injuries could be estimated for Mississippi and Alabama ranging from 0.2% to 4.2% of secondary and tertiary productivity lost over three years, depending on the habitat investigated and its spatial location in the study area. The analysis demonstrates the effectiveness of the AQUATOX model as a tool to quantify levels of injury by comparing the results of a baseline ecological model, calibrated and verified with pre-oiling observations, with post-oiling results. This alternative approach to injury assessment can be used to validate single-species approaches and also to evaluate the injury to, and recovery of, an integrated ecosystem