Benthic Invertebrate Populations Research Articles

Extreme population densities reduce reproductive effort of Atlantic sea scallops in high-density recruitment events

The Atlantic sea scallop Placopecten magellanicus supports one of the most valuable federal fisheries in the USA, with annual ex-vessel values of US$400-600 million since 2010. Among other strategies, the fishery utilizes rotational area management to protect juvenile sea scallops, increasing yield per recruit and spawning potential. While generally successful, area management was challenged by 2 extremely high-density recruitment events. Juveniles at both study sites, the Nantucket Lightship Closed Area and the Elephant Trunk portion of the Mid-Atlantic Access Area, persisted at high densities (up to 39 and 5 sea scallops m-2, respectively) and initially exhibited poor growth, yield, and gamete production. The effect of sea scallop population density on reproduction was investigated through quarterly sampling from May 2018 through January 2020 in low-, medium-, and high-density strata. Reproductive effort, i.e. the proportion of energy devoted to gamete production, was quantified to investigate differences in energy allocation across density, depth, shell height, reproductive stage, and sex. Reproductive activity was limited in the Nantucket Lightship high-density stratum, where the percentage of sea scallops staged as mature or spawning reached 50% during only 1 of 7 sampling trips, compared to 4-6 sampling trips in other strata. Population density was a significant predictor of reproductive effort, with a 28% reduction in reproductive effort from the highest densities to more typical densities. These results illustrate the complexities of managing fisheries for heterogeneous populations of sessile benthic invertebrates. Negative density-dependent effects should be monitored and accounted for in future extreme recruitment events.

The prey availability and diet of juvenile Atlantic salmon (Salmo salar L.) in low-productivity rivers in northern Europe.

The availability of resources varies across a species distributional range, and a low-productivity area can make a species more vulnerable. We investigated the invertebrate composition and prey choice of juvenile Atlantic salmon (Salmo salar L.) in low-productivity rivers in northeast Iceland, which is one of the species' most northerly distributions. By sampling benthic and drift invertebrate populations, we found that prey availability was similar within and between rivers. Gut content samples showed that the main prey choice for juvenile S. salar was the Chironomidae. The type of food items consumed varied across different weight groups of S. salar, with smaller juveniles having more diverse diet. S. salar did not have a selection preference for chironomids, which indicates that they were eating the highly available prey in their environment, rather than hunting high biomass items such as terrestrial invertebrates and large Dipterans. Estimates of dietary niche showed that S. salar in these low-productivity rivers relied on consuming what was most readily available, the chironomids, and that they must share resources with other salmonid species. This may be due to the low diversity of freshwater invertebrates (fewer prey options), whereas S. salar in nutrient-rich rivers could rely more on terrestrial invertebrates as an additional subsidy in their diet. In conclusion, with limited prey choices, juvenile S. salar in nutrient-poor rivers, especially in a biogeographically isolated region with low species diversity, may increase in vulnerability and decrease in adaptability to environmental change. Management methods that increase benthic prey abundance and diversity are recommended for conserving the S. salar population in a nutrient-poor river.

Hypothesised life cycle adaptation of stonefly (Plecoptera) in response to increased water temperatures

Water temperature is the most important and critical factor for freshwater invertebrates and it fluctuates with an increase in air temperature. In this study, the effect of water temperature on egg development was clarified in Stavsolus japonicus, and the response to climate change in stoneflies with long egg periods were considered. Water temperatures prior to 43 days before hatching likely do not affect egg development in Stavsolus japonicus. Instead, they use egg diapause as an adaptive strategy to survive hot summer conditions. Increased water temperatures may cause migration to higher elevations for stoneflies that have lower adaptability in their egg development period, with populations eventually becoming stranded where no higher elevation or cooler habitat is available. Species extinction is expected to increase with increasing temperatures, leading to reduced biodiversity in many ecosystems. Indirect effects of water warming on maturation and reproduction may lead to substantial reductions in benthic invertebrate populations.

Islands in the mud: The South Texas banks provide crucial mesophotic habitat for coral communities

On the continental shelf off the coast of South Texas lie a series of natural hard-bottom structures (rocky outcrops and relic coral-algal reefs) known as the South Texas Banks (STB), which provide critical habitat for benthic organisms and pelagic fish. The depth of the banks, a persistent nepheloid layer, and strong currents have resulted in few studies that provide quantitative biodiversity data on the STB. Using a remotely operated vehicle (ROV), video surveys were conducted to quantitatively describe the mesophotic coral communities and assess habitat suitability of five STB: North Hospital, Hospital, Southern, Big Adam, and Mysterious Banks. Each of these STB have significantly different benthic communites, with coral communities composed primarily of antipatharians and octocorals. Big Adam Bank had the lowest biodiversity and the least coral cover. Mysterious Bank had abundant antipatharians, specifically Stichopathes spp., but low biodiversity overall. Hospital Bank had low coral diversity that was offset by high diversity in sponges and other invertebrate species. North Hospital and Southern Banks had abundant and diverse populations of coral species, including scleractinians, and other benthic invertebrates. These data indicate that the STB are crucial islands of biodiversity in an area with few suitable areas for coral reef species. In addition, predictive modelling of habitat suitability provided valuable estimates on the potential distribution of key benthic community members, such as scleractinians and antipatharians, throughout the entire areas of the five banks assessed.

Larval dispersal and recruitment of benthic invertebrates in the Arctic Ocean

Larval dispersal is a fundamental process responsible for colonization and connectivity of benthic invertebrate populations. It is difficult to study larval dispersal in polar environments because weather and climate conditions restrict sample collection to certain seasons. In this study, we leveraged oceanographic moorings as long-term scientific platforms for collecting larvae and recruits of benthic invertebrate species in the Fram Strait and along the continental slope north of Svalbard in 2017–2021. Larval traps and fouling panels were deployed at various depths on 15 moorings at 8 locations, and additional specimens of biofouling were obtained opportunistically from moored instruments. Our results showed a significant difference in species composition between samples collected in Atlantic Water in the West Spitsbergen Current (WSC) and samples collected in Arctic Water near the seafloor and in the East Greenland Current (EGC) in the western part of the Fram Strait. There was also a stark difference between Atlantic Water species in the Fram Strait and on the north Svalbard slope. Most specimens collected in the WSC belonged to species with long-duration planktotrophic larvae, such as the ubiquitous bivalve Hiatella arctica, the bryozoan Alcyonidium mamillatum, and two nudibranchs. Samplers exposed primarily to Arctic water at their given depth and location were dominated by hydrozoans. We observed medusae budding off of the hydroids Stegopoma plicatile and Rhizoragium roseum. Our study demonstrates that the WSC is an important vector for larval dispersal into the central Arctic Ocean. Integration of biological samplers on oceanographic moorings holds great promise for monitoring efforts as climate change progresses, especially in environments where research is challenging and seasonally limited, such as the Arctic.

The behavior of Gammarus aequicauda (crustacea, amphipoda) during predation on chironomid larvae: Sex differences and changes in precopulatory mate‐guarding state

The foraging behavior determines the diet size influencing the growth and reproduction of a predator and its prey populations. Amphipods play a key role in various aquatic ecosystems. Gammarus aequicauda is an abundant widespread omnivorous species and the only known amphipod species of hypersaline waters. Its predation can suppress the populations of planktonic and benthic invertebrates. Males of G. aequicauda actively eat chironomid larvae but there is no data on predatory females. Experiments were conducted to study sex-related differences in feeding behavior including during precopulatory mate guarding (PCMG). There were significant sex differences in feeding characteristics. For females, calculations showed that maximum consumption could be 3-4 chironomid larvae per day and for males about 9-10 larvae per day. During PCMG, males did not feed and females fed as efficiently as single females. Males transported females and alone carrying the energetic costs of swimming during PCMG. Less expenditure of energy on swimming means more energy for reproduction for females. This allows more energy-efficient use of food resources and increases the reproductive success of the population. There are currently two alternative views on PCMG among crustaceans. 1. It is a sexual conflict between males and females serving as a male adaptive strategy to achieve a female during strong male competition, while females bear many costs during the long guarding period. 2. There is also the opposite view that pairs get energetic benefits from long PCMG. Obtained data suggest that PCMG is likely to be intersexual cooperation and not intersexual conflict.

Long-term trends in benthic invertebrate populations (1929–2013) in Lake Winnipeg

Abstract Spatial, seasonal, and inter-annual variation in zoobenthos was examined in Lake Winnipeg which has experienced accelerated nutrient loading and multiple environmental stressors over the last several decades leading to increased overall productivity. Qualitative zoobenthos data (1928–29) and quantitative data (1969–2013), revealed two prevailing patterns: (1) a substantial increase in density, mainly Oligochaeta (Tubificinae), Mollusca (Sphaeriidae), and Diptera (Chironomidae) in the North basin, but a less consistent pattern of increase in density overall and of Ephemeroptera (Ephemeridae) and Trichoptera (Leptoceridae) in the South basin, and (2) disappearance of Amphipoda ( Diporeia ) from the South basin and a decline in Diporeia as a dominant taxon in the North basin, although it remained prevalent in the Narrows where higher total organic carbon (TOC) concentrations have persisted. Permutational analysis of variance (PERMANOVA) revealed that over time, inter-basin variation overwhelmed the seasonal component of variation in zoobenthos abundance. The benthic environment has changed (e.g. food resources, sediment particle sizes and nutrients) over the decades, contributing to the substantial changes in zoobenthos abundance and community composition that may constitute a regime change in the lake.

Do larval types affect genetic connectivity at sea? Testing hypothesis in two sibling marine gastropods with contrasting larval development

In marine environments, connectivity among populations of benthic invertebrates is provided primarily by dispersion of larvae, with the duration of pelagic larval phase (PLD) supposed to represent one of the major factor affecting connectivity. In marine gastropods, PLD is linked to specific larval development types, which may be entirely intracapsular (thus lacking a pelagic dispersal), or include a short pelagic lecithotrophic or a long planktotrophic phase.In the present study, we investigated two sibling species of the cosmopolitan neogastropod genus Columbella (commonly known as dove shells): Columbella adansoni Menke, 1853, from the Macaronesian Atlantic archipelagos, with planktotrophic development, and Columbella rustica Linnaeus, 1758, from the Mediterranean Sea, with intracapsular development.We expected to find differences between these two sister species, in terms of phylogeographic structure, levels of genetic diversification and spatial distribution of genetic diversity, if PLD was actually a relevant factor affecting connectivity.By analysing the sequence variation at the cytochrome c oxidase subunit I (COI) in 167 specimens of the two species, collected over a comparable geographic range, we found that Columbella adansoni, the species with planktotrophic development, and thus longer PLD, showed no phylogeographic structure, lower levels of genetic diversity, interpopulational variance lower than the intrapopulational one and no spatial structure in the distribution of the genetic diversity; Columbella rustica, the species with intracapsular development, thus with evidently lower dispersal abilities, showed a clear phylogeographic structure, higher levels of genetic diversity, high interpopulational and low intrapopulational variance, and a clear signature of global spatial structure in the distribution of the genetic diversity.Thus, in this study, two sibling species differing almost only in their larval ecology (and PLD), when compared for their genetic variation showed patterns supporting the hypothesis that PLD is a major factor affecting genetic connectivity.Therefore, it seems reasonable to expect that the ecological attributes of the marine communities - also in terms of the variation in larval ecology of the species involved – are taken into the due consideration in conservation actions, like the design of marine protected areas networks.

Testing microbial pathogens as a cause of early juvenile mortality in wild populations of benthic invertebrates

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 562:53-63 (2016) - DOI: https://doi.org/10.3354/meps11975 Testing microbial pathogens as a cause of early juvenile mortality in wild populations of benthic invertebrates Samantha D. Sandee, Jonathan D. Van Hamme, Louis A. Gosselin* Department of Biological Sciences, Thompson Rivers University, 900 McGill Road, Kamloops, BC V2C 0C8, Canada *Corresponding author: lgosselin@tru.ca ABSTRACT: Microbial pathogens such as bacteria, viruses, fungi, and protozoa are potentially important causes of mortality during the critical first days of juvenile life in benthic invertebrates, but their effect on early juveniles in natural habitats remains unexplored. We therefore placed newly-settled mussels (Mytilus trossulus) and barnacles (Balanus glandula, Chthamalus dalli), and newly-hatched snails (Nucella ostrina) in screened cages submerged in the field, exposing them to ambient microbial organisms while isolating them from most non-microbial mortality factors. Mortality over a 5 d period was only 0-3% in M. trossulus and N. ostrina and 0-10% in B. glandula and C. dalli. Mortality was consistent among replicate trials in the same summer and between 2 different years, and was much lower than previously reported natural early juvenile mortality in these species. We then examined whether bacterial infection caused the few juvenile deaths in our field experiment. Dosage testing in the laboratory with 5 antibiotics resulted in an antibiotic cocktail providing broad-spectrum antibacterial protection without affecting the health of juveniles. In a second field experiment, early juvenile M. trossulus and N. ostrina exposed to the antibiotic cocktail 3 times daily did not experience reduced mortality relative to controls. Our findings suggest that, at least in some species, microbial pathogens are not a direct cause of juvenile mortality in the field, thus narrowing the list of potential causes of early juvenile mortality to the non-microbial factors excluded from our experiments. KEY WORDS: Early benthic phase · Natural mortality · Bacteria · Viruses · Antibiotics · Immune response · Survivorship · Mussels · Barnacle cyprids · Snails Full text in pdf format PreviousNextCite this article as: Sandee SD, Van Hamme JD, Gosselin LA (2016) Testing microbial pathogens as a cause of early juvenile mortality in wild populations of benthic invertebrates. Mar Ecol Prog Ser 562:53-63. https://doi.org/10.3354/meps11975 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 562. Online publication date: December 29, 2016 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2016 Inter-Research.

Analysis of benthic invertebrate communities downstream of land-based aquaculture facilities in Nova Scotia, Canada

AbstractLand-based aquaculture facilities are located throughout Nova Scotia. They are generally located beside streams, to which they discharge large quantities of used water, and their discharges are usually only monitored for some nutrient parameters at varying frequencies. However, intermittent water sampling is not sufficient to assess any aquatic ecosystem health impacts resulting from discharges. Monitoring benthic invertebrate populations’ characteristics can be used to assess aquatic ecosystem health, and this study evaluated the benthic invertebrate population characteristics downstream of five land-based aquaculture facilities in Nova Scotia. Total abundance and relative abundance of Chironomidae were elevated, while number of taxa, relative abundance of Ephemeroptera + Plecoptera + Trichoptera (EPT), Pielou’s evenness and diversity were reduced at three out of the five sampling locations. Furthermore, a comparison of populations of benthic invertebrates downstream of the facilities to those pr...

Diversity and distribution within the sea spider genus Pallenopsis (Chelicerata: Pycnogonida) in the Western Antarctic as revealed by mitochondrial DNA

Pycnogonids are marine arthropods with cosmopolitan and eurybathic distribution. Of the approximately 1300 pycnogonid species described worldwide, over 260 species occur in the Southern Ocean, and over half of those are endemic to the Antarctic. Morphological data suggest circumpolar distributions for multiple Antarctic species; however, recent molecular inquiries into the genetic structure of Antarctic benthic invertebrate populations have revealed varying patterns of genetic connectivity and, in many cases, radiation of morphologically cryptic species incompatible with the previously hypothesized genetic homogeneity for Southern Ocean invertebrates. To date, little is known about genetic connectivity within Antarctic Pallenopsis species populations, and Pallenopsis phylogeny remains poorly resolved. This study describes genetic structure of Pallenopsis populations of western Antarctic coastal regions, the Scotia Arc, Falkland Islands, and Chilean coast. We present the results of analyses derived from the mitochondrial COI gene that demonstrate patterns of connectivity for these populations. Examination of genetic characters has allowed for the identification of divergent mitochondrial lineages within Pallenopsis and will lead to a description of at least one new species. Future sampling and analyses from other areas of the Antarctic coastline will provide a broader context for the phylogeny of Pallenopsis.

Vulnerability of marine benthic metapopulations: implications of spatially structured connectivity for conservation practice in the Gulf of Lions (NW Mediterranean Sea)

AbstractAimEcological connectivity is currently considered to be essential to enhance biodiversity conservation efforts and benefit adjacent areas. We evaluate the spatial structure of vulnerable marine benthic invertebrate populations based on connectivity to improve the placement of marine protected areas.LocationGulf of Lions, NW Mediterranean Sea.MethodsWe used a spatially explicit metapopulation model to explore how larval dispersal affects marine benthic invertebrate dynamics at local and regional scales. Minimum recruitment success (the proportion of larvae that settle in a site and survive between spawning and first reproduction, which is required to ensure species persistence) is proposed as a measure of vulnerability. Three contrasting simulations were constructed: closed versus connected populations, habitat loss versus recruitment failure disturbances and varying patterns of oceanographic connectivity. The rescue factor (the ratio of minimum recruitment success in connected and closed populations) quantified the decrease in vulnerability because of oceanographic connectivity.ResultsIn the Gulf of Lions, connectivity reduced population vulnerability by a rescue factor of 5.3. The minimum recruitment success for regional persistence decreased from 3% to 0.2% when species' life expectancies increased from 2 to 50 years. Connectivity enabled the spread of individuals over the entire region, but there were higher densities in sink sites, where low retention rates do not allow for local persistence (western tip of the gulf). Source sites, defined as those sites bringing metapopulation resistance to recruitment failure and stresses from habitat loss, were located in the centre of the gulf.Main conclusionsConnectivity drives the spatial structure of population density distribution and population vulnerability in the absence of any other structuring factor. In the Gulf of Lions, marine protected areas are located in population sinks; however; if protection measures were taken in the central part, populations would benefit throughout the region via the rescue effect.

Short-term effects of bottom trawling and a storm event on soft-bottom benthos in the eastern Bering Sea

AbstractA Before–After Control–Impact (BACI) experiment was conducted to investigate the effects of a commercial bottom trawl on benthic invertebrates in a sandy and previously untrawled area of the eastern Bering Sea. Six pairs of experimental and control corridors were sampled with a research trawl before and after four consecutive tows with the commercial otter trawl. A major storm event occurred during the experiment, and it was possible to differentiate its effect from that of the trawling using the BACI model. Species composition changed very little; Asterias amurensis and Paralithodes camtschaticus comprised over 80% of the total invertebrate biomass (kg ha−1) during each year of the study. In general, the commercial trawl did not significantly affect the biomass of the benthic invertebrate populations. The trawling effect after 4–14 d was statistically significant in three of the 24 taxa that were analysed, which was, as expected, because of nothing more than random variation with α = 0.10. Biomass immediately after the trawling disturbance was lower for 15 of the taxa and higher for the other nine, with a median change of −14.2%. Similarly, the effect of trawling on invertebrate biomass after one year was not statistically significant for any of the taxonomic groups (p ≥ 0.23), indicating no evidence of a delayed response to the commercial-trawl disturbance. Further analysis suggests that storms have an overall greater effect on the benthos than do bottom trawls at this location. Both the numbers of taxa significantly affected by trawling and the storm (3 vs. 12), as well as the median sizes of these effects −14.2% vs. −22.0%), were greater for the storm event. Results from this study are combined with those from a related investigation of chronic trawling effects to propose an adaptive management strategy for the study region, including rotating area closures to mitigate for temporary trawling effects.

Epifaunal invertebrates as predators of juvenile bay scallops (Argopecten irradians)

Predation strongly influences populations of numerous benthic invertebrates, although many predation studies to date have focused on macroscopic individuals, ignoring critical early life stages. Juveniles of the bay scallop, Argopecten irradians, settle and grow on the blades of eelgrass, Zostera marina, then migrate to the sediment surface when their mobility and size provide a refuge from benthic predators. During their time in the eelgrass canopy, scallops co-occur with a diverse array of small invertebrates, including peracarid and small decapod crustaceans, whose role as predators is largely unexplored. We measured consumption by amphipods, isopods, and a shrimp on recently settled bay scallops ranging in size from 0.5 to >1.5mm in a series of 24-hour experimental laboratory assays. These invertebrate predators, which were common concurrent epifaunal surveys of restored eelgrass beds in the mid-Atlantic, consumed up to 63% day−1 of juvenile scallops when the scallops were <1mm, but predation impacts decreased as scallops exceeded this size. Our data have implications for current restoration of both bay scallops and their eelgrass habitat, suggesting that previously unrecognized consumers may significantly affect scallop population dynamics at early life stages.

A MODEL INCORPORATING DISTURBANCE AND RECOVERY PROCESSES IN BENTHIC INVERTEBRATE HABITAT—FLOW TIME SERIES

ABSTRACTWe describe and demonstrate a model (Benthic Invertebrate Time Series Habitat Simulation) for calculating the effect of changes to flow regimes on benthic invertebrate habitat and population dynamics. The following inputs are required: a hydrograph (discharge time series), habitat–discharge relationship, disturbance–discharge relationship, wetted width–discharge relationship and a recolonization time series. Habitat–discharge, disturbance–discharge and wetted width–discharge relationships are common outputs from instream hydraulic habitat models (e.g. Physical Habitat Simulation, River Hydraulic Habitat Simulation and River2D). Hydraulic habitat models calculate a combined habitat suitability index from physical habitat suitability curves for water depth, velocity and substrate composition and weight this by area to give a weighted usable area (WUA). Because conventional invertebrate habitat suitability curves are based on density estimates, the combined habitat suitability index can be treated as an index of density and WUA treated as an index of potential relative abundance (at the reach scale) in the absence of disturbance due to flow variation (flooding and drying) and biotic processes. Our approach begins with WUA and calculates realizable suitable habitat (i.e. relative abundance) by taking into account the resetting of benthic invertebrate densities by floods and drying and recovery (or accrual) rates and times. The approach is intended mainly to compare the relative amounts of productive invertebrate habitat sustained by natural and modified flow regimes, but it also has the potential for investigating the influence of flow variation on invertebrate population dynamics. We anticipate that the model will be particularly useful for assessing effects of changes in flow regimes caused by diversions, abstractions or water storage on annual benthic invertebrate productivity. Copyright © 2013 John Wiley &amp; Sons, Ltd.

Bioconcentration of benzo[a]pyrene in Chironomus riparius and Lumbriculus variegatus in relation to dissolved organic matter and biotransformation

The relative health of benthic invertebrate populations is threatened by both dissolved and strongly-bound contaminants. Sediment-bound contaminants can be mobilized and metabolized in the guts of deposit-feeders and may lead to even more potent derivatives. For this reason, measures of parent substance concentrations in organisms are not a suitable exposure indicator when substantial biotransformation can occur. In this study, we assessed the concentration of waterborne 14C-benzo[a]pyrene (BaP) in Chironomus riparius larvae and in the oligochaete Lumbriculus variegatus at different levels of dissolved organic carbon (DOC). These two species have different biotransformation capabilities. Polydimethylsiloxane (PDMS) fiber was used to assess the freely-dissolved concentrations for the prediction of uptake and elimination kinetics. Exposure concentrations decreased due to the presence of DOC. Radioactivity that corresponded to the metabolites exceeded 90% of total extractable fractions in C. riparius, and suggested that BaP metabolism was faster than uptake from solution. However, only 10% of the extracted activity was attributed to metabolites in L. variegatus. Measured tissue concentrations and model-predicted uptake and elimination rates showed that L. variegatus mainly accumulated parent compound, whereas C. riparius accumulated mainly metabolites. No effect of DOC was observed on the biotransformation of BaP in either species.

A Quantitative Post-Release Evaluation of Biological Control of Water Lettuce,Pistia StratiotesL. (Araceae) by the WeevilNeohydronomus AffinisHustache (Coleoptera: Curculionidae) at Cape Recife Nature Reserve, Eastern Cape Province, South Africa

Water lettuce, Pistia stratiotes L. (Araceae) is recognized as being among the world's worst aquatic weeds. In its adventive range, the plant forms extensive mats capable of blocking navigation channels, impeding water flow in irrigation and flood control canals, and disrupting hydropower generation (Holm et al. 1977). Dense mats of the weed prevent light penetration into the water column which negatively affects submerged aquatic plant communities, causing a lowering of the oxygen concentration and thereby reducing benthic invertebrate and fish populations (Neuenschwander et al. 2009).

Identifying the causes of sediment‐associated contamination in the Illinois River (USA) using a whole‐sediment toxicity identification evaluation

Whole-sediment toxicity identification evaluation (TIE) techniques were employed on the Illinois River Complex (IRC), USA to identify the sources of sediment toxicity that may have contributed to the decline in benthic invertebrate populations. The TIE focused on three classes of contaminants: ammonia, metals, and organics. Sediment toxicity was assessed using the amphipod Hyalella azteca, and the focus of the TIE was on assessing spatial and temporal patterns of contamination. Past studies suggested that ammonia was the major source of contamination in IRC sediments. However, the present study suggested that polycyclic aromatic hydrocarbons (PAHs) were the primary contributor to sediment toxicity. Phase I testing showed 46% of the site trials (12 of 26) exhibited increased H. azteca survival (p < 0.05) with the addition of powdered coconut charcoal (organic amendment), whereas zeolite (ammonia amendment) and Resin Tech SIR 300 (cationic metals amendment) did not increase H. azteca survival. Phase II testing revealed PAH concentrations were high enough to cause the observed toxicity, confirming phase I results. Spatially, sediment toxicity as well as pore-water ammonia concentrations declined with distance downstream from suspected contaminant sources, indicating a potential dilution or remedial effect. Temporally, pore-water ammonia, metals, and PAH concentrations varied among sampling periods over an annual cycle for some sites near urbanized areas, while remaining temporally consistent at others. The results of the present study provide new information on the sources of toxicity within the IRC, and demonstrate the importance of evaluating spatial and temporal aspects in sediment TIEs. This is particularly important for evaluations in riverine systems in which hydrologic processes can result in large variation in sediment toxicity on temporal and spatial scales.

Deep-sea octocorals and antipatharians show no evidence of seamount-scale endemism in the NW Atlantic

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 397:25-35 (2009) - DOI: https://doi.org/10.3354/meps08318 Deep-sea octocorals and antipatharians show no evidence of seamount-scale endemism in the NW Atlantic Jana N. Thoma*, Eric Pante*, Mercer R. Brugler, Scott C. France** University of Louisiana at Lafayette, Department of Biology, PO Box 42451, Lafayette, Louisiana 70504, USA *Jana N. Thoma and Eric Pante have contributed equally to this project**Corresponding author. Email: france@louisiana.edu ABSTRACT: Seamounts are undersea mountains commonly characterized by accelerated currents, exposed hard-substrates, and relatively high biomass and biodiversity. Hydrographic features associated with seamounts have led authors to hypothesize that benthic invertebrate populations from geographically separated seamounts (and the continental slope) may experience varying degrees of genetic isolation, resulting in high levels of endemism. While this hypothesis has been tested for multiple taxonomic groups in the Pacific, it has rarely been addressed in the Atlantic. We tested the null hypothesis that the geographic ranges of corals from NW Atlantic seamounts are restricted to individual seamounts. We examined 188 octocoral and 50 antipatharian colonies (representing 6 and 2 genera, respectively) from 14 seamounts, spanning 1700 km, and the adjacent continental margin and estimated their genetic variation using mitochondrial loci (msh1 for all octocorals, as well as an intergenic region for isidids, and 3 multi-gene spanning segments for antipatharians). Well-sampled haplotypes were not geographically isolated on individual seamounts, thus refuting the hypothesis of local endemism of coral fauna on the New England and Corner Seamounts. The narrow geographic distribution of rare haplotypes is most likely due to undersampling rather than endemism. Our results do not preclude that cryptic variation and endemism not revealed by mitochondrial DNA may become evident should more variable markers be developed. KEY WORDS: Endemism · Biogeography · Marine connectivity · Dispersal · Chrysogorgiidae · Paramuricea · Black coral · Anthozoa Full text in pdf format Supplementary material PreviousNextCite this article as: Thoma JN, Pante E, Brugler MR, France SC (2009) Deep-sea octocorals and antipatharians show no evidence of seamount-scale endemism in the NW Atlantic. Mar Ecol Prog Ser 397:25-35. https://doi.org/10.3354/meps08318Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 397. Online publication date: December 17, 2009 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2009 Inter-Research.

Spatial patterns in recruitment and growth of the mussel Mytilus californianus (Conrad) in southern and northern California, USA, two regions with differing oceanographic conditions

Mussels, Mytilus californianus, and other benthic invertebrate populations on the wave-exposed intertidal coast of the eastern North Pacific are impacted by a suite of biotic and abiotic factors on both local and larger geographic scales. Previous surveys of mussel abundances along the California coast have revealed that mussels, in general, are very abundant in northern California while low in southern California. Nevertheless, mussel abundances in southern California are highly variability with a small number of sites that are characterized as having moderately high to high abundances. To elucidate driving factors of mussel abundances in these regions, we investigated recruitment and growth rates of mussels in 1) northern and southern California, two regions separated by ca. 900 km and exposed to vastly different oceanographic processes and 2) within southern California at sites with moderately high mussel abundances and at sites with low abundances. We found that recruitment and, to a degree, growth may be important factors driving variable abundances of mussels within southern California but could not explain patterns along the entire California coast. Recruitment and growth rates were low in northern California even though mussels were highly abundant. Conversely, recruitment and growth in southern California were significantly higher than northern California and, within the region, were higher in sites characterized by moderately high abundances. Among regions, differences in recruitment and growth are likely driven by large scale oceanographic patterns such as upwelling affecting larval transport and temperature affecting growth. Within southern California, local oceanographic processes likely enhanced or inhibited recruitment or growth leading to differences in measures between closely located sites.