A Revised Key to Leptocaris (Copepoda: Harpacticoida), Including a New Species From a Shallow Estuarine Lake in Louisiana, USA

During ecological research of benthic and fouling assemblages in a shallow estuarine lake in central Louisiana receiving thermal effluent, a new species of harpacticoid copepod was discovered. Approximately 700 specimens of Leptocaris kunzi n. sp. were collected on artificial substrate plates from August, 1977 - January, 1978. This new species is herein described and illustrated. Leptocaris kunzi n. sp. differs from other members of the nominal genus in the setation of the P2 - P4 endopods and by having a female P5 not fused into a single plate. The most closely related species to L. kunzi n. sp. appear to be L. elishevae (Por) and L. canariensis Lang. A revised key to the genus is presented

Grass shrimp Palaemonetes pugio predation on sediment- and stem-dwelling meiofauna: Field and laboratory experiments

Field and laboratory experiments were conducted to clarify the predatory role of Palaemonetes pugio Holthius in salt-marsh benthic communities. Field experiments (cage enclosures using P. pugio as a predator) were conducted on unvegetated mudflat and vegetated-marsh sites. Neither sediment- or stem-dwelling meiofaunal abundances were significantly impacted. Laboratory experiments measured the functional response of P. pugio feeding on suspended harpacticoid copepods, tested the efficiency of P. pugio feeding on harpacticoids in sediments, and measured the predation rate of P. pugio on stem-dwelling meiofauna. Grass shrimp feeding rate on suspended copepods followed a type II functional response, increasing with increasing prey density to a maximum of 59 copepods h-1. When a sediment refuge was available, a 40% decline in the consumption of copepods by P. pugio was noted; this decreased feeding efficiency may contribute to the lack of significant declines in meiofaunal abundances in field enclosures over unvegetated sediment. P. pugio proved to be a highly effective predator on the fauna of Spartina alterniflora stems, significantly reducing abundances of stem-associated meiofauna within 24 h and consuming an estimated 35 meiofauna h-1. The greatest impact was exhibited on the lowest (0 to 6 cm) portion of the stems. These experiments suggest that laboratory experiments are an important aid to help interpret field experiments examining predation on meiofauna, and that Spartina stems, and their epiphytic algae and meiofauna, are important, but largely overlooked, resources in salt-marsh food webs

Genetic diversity in a deep-sea harpacticoid copepod found near two oil-drilling sites in the gulf of mexico

Sites adjacent to (near-field) and distant from (far-field) oil-drilling platforms were sampled for harpacticoid copepods at two locations in the northern Gulf of Mexico off the coast of Louisiana, both at depths of ≈ 1100 m. The sites were located at Garden Banks Area Block 602 (GB 602) and Mississippi Canyon Area Block 292 (MC 292). Near-field sites at both locations were characterized by large numbers of a single undescribed species of harpacticoid copepod, Bathycletopsyllus sp., but this species was essentially absent from far-field sites. We sequenced a 710 bp portion of the mitochondrial cytochrome c oxidase subunit I gene (COX I) to analyze the genetic diversity and population structure of Bathycletopsyllus sp. at the two platforms, and to determine if the harpacticoids examined were either a single species, or a complex of cryptic species. We found that divergence at the COX I gene (maximum 1.6) was within the range observed for intraspecific variability in previously-studied species of harpacticoid copepods that were well-characterized taxonomically. Thus, the two samples analyzed here were a single species and not a complex of cryptic species. In addition, there was significant genetic heterogeneity between the two samples, suggesting limited gene flow between the two sites. This was expected given the low dispersal potential typical of harpacticoids and the distance between the sites (407 km). Lastly, haplotype diversity and nucleotide diversity were both low in the GB 602 sample, giving a nominally-significant departure from a pure neutral model. This result could indicate the occurrence of selective sweeps, temporal population size variation or other processes not included in the neutral model. In contrast, haplotype diversity and nucleotide diversity were both higher in the MC 292 sample than at Garden Banks, and there was no detectable departure from neutrality. For both samples, diversity at the haplotype and nucleotide levels were within the range seen in shallow-water harpacticoid species inhabiting both uncontaminated and contaminated muddy sediments, so there was no evidence for pollution related effects in the present study. © 2010 The Crustacean Society

Mummichog Fundulus heteroclitus responses to long-term, whole-ecosystem nutrient enrichment

Author Posting. © The Author(s), 2013. This is the author's version of the work. It is posted here by permission of Inter-Research for personal use, not for redistribution. The definitive version was published in Marine Ecology Progress Series 492 (2013): 211-222, doi:10.3354/meps10495.The effects of eutrophication on coastal plants and sessile animals are becoming well known, but responses of mobile species are less well studied. Here, we link variation in abundance, biomass, body size, growth rate, and resource utilization in mummichogs (Fundulus heteroclitus) > 40 mm in length to experimental nutrient enrichment in Plum Island Sound, Massachusetts, USA. To mimic cultural eutrophication, dissolved fertilizer was released into replicate saltmarsh creeks on each rising tide throughout entire growing seasons. In the summer of the 6th year of enrichment, we released coded-wire tagged mummichogs into nutrient-enriched (n = 3733 fish) and reference (n = 3894 fish) creeks and recaptured them over the next two months. We found increased abundance (by 37%), biomass (58%), body size (8%), and herbivory (115%, measured as photosynthetic gut pigment content) in nutrient-enriched creeks, although body condition was unaffected. However, individual growth rates were 43% lower in nutrient-enriched creeks. Nutrient enrichment stimulated primary production causing a bottom-up enrichment of the food web, which fostered increased biomass and body size. However, the reduction in growth rate indicates an adverse consequence of long-term nutrient enrichment. This negative effect occurred in the absence of increased hypoxia in these highly tidally (4-m amplitude) flushed study creeks. The mummichog is an important predator/grazer in salt marshes, and nutrient-induced alterations in biomass or resource utilization will directly or indirectly affect lower trophic levels, including benthic algae, thereby impacting the 63 ecosystem-wide response to eutrophication.This material is based upon the work supported by the National Science Foundation under Grant Nos. 0816963, 0923689 and 0423565

Effects of habitat complexity and hydrodynamics on the abundance and diversity of small invertebrates colonizing artificial substrates

Invertebrate colonization in a shallow estuarine embayment was studied with the use of artificial substrates (bottle brushes) to create and mimic complex habitats. Substrates were manipulated to obtain varying levels of habitat density and surface area by shortening and/or removing bristles from the brushes. Complexity was quantified as the total surface area of bristles and bristle surface area within the geometric volume of the substrate (i.e., bristle density). Short-bristled brushes provided greater habitat density while long-bristled brushes provided larger surface area within the same removal treatment. Abundance of invertebrates that recruited from the water column (mostly from the meiobenthos) averaged 2500–7000 individuals per collector after 10 days, and abundances significantly increased with increasing habitat density (i.e., decreasing bristle removal). The abundance of nematodes and copepod species richness were more closely related to bristle density than surface area. Copepod abundance was more closely related to surface area than bristle density. Flow visualizations in a paddlewheel flume revealed that water was diverted around brushes with high bristle density (0% and 20% bristle removal), regardless of bristle length, when incident flow was 6 cm s−1. Relatively more water passed through the brushes in low bristle density treatments (80% removal) and when freestream velocity was increased to 12 cm s−1. Measurements of flow speed on the upstream and downstream sides of brushes confirmed that fractional transmission of velocity (transmissivity) increased with freestream velocity, but showed inconsistent patterns among length and removal treatments. Flow was substantially decreased by interaction with the brushes, which probably enhanced the retention of invertebrates. The dissimilar responses of nematodes and copepods suggest that not all small taxa respond to the same components of architectural complexity and that there are both physical and biological components to recruitment of these artificial substrates

Response of a benthic food web to hydrocarbon contamination

Direct and indirect effects of diesel-contaminated sediment on microalgae, meiofauna, and meiofauna-microalgae trophic interactions were examined in a microcosm study of the sediment community from a Spartina alterniflora salt marsh. Microcosms of natural sediment were given small dally doses of contaminated sediment over a 28-d period, creating low-, medium-, and high-diesel treatment concentrations of ~ 0.5, 5.5, and 55 ppm PAH, respectively. Diesel caused initial (within 7 h) reductions in microalgal grazing by meiobenthic harpacticoid copepods. Over longer periods of exposure (7-28 d), grazing on microalgae by copepods as a group was reduced in high-diesel treatments, primarily because of high copepod mortality. In contrast, grazing by and abundance of Cletocamptus deitersi (a copepod) was significantly enhanced in high-diesel treatments. Concurrent with reduced grazing by copepods, nematode grazing rates increased significantly in high-diesel treatments, indicating possible competition for microalgae between copepods and nematodes. In spite of transiently enhanced grazing by nematodes and C. deitersi, total meiofaunal grazing on microalgae was reduced in high-diesel treatments. Increased Chl a : pheopigment ratios in contaminated sediments were also indicative of reduced grazing pressure. A large (10x) increase in microalgal biomass was observed in high-diesel treatments and was likely a consequence of reduced meiofaunal grazing. The general responses observed in microcosms were also observed in a field study of polycyclic aromatic hydrocarbon contamination. Collectively, our data indicate that benthic microalgal biomass is controlled by meiofaunal grazing and that meiofauna may compete for limited algal resources. Furthermore, consideration of multiple trophic levels and their interactions allows a more complete and ecologically meaningful understanding of the mechanisms by which contaminants induce changes in natural communities

Preliminary Evaluation of the Use of Phosphogypsum for Reef Substrate in the Gulf of Mexico

Phosphogypsum (PG), a solid by-product of phosphoric acid production in the fertilizer industry, contains radionuclides and trace metals in concentrations which are potentially hazardous to human health and to the environment. Due to the presence of these contaminants and to the lack of safe alternative uses for PG, the industry has necessarily resorted to on-site stockpiling as the primary disposal method. Thirty-three such stockpiles, totaling millions of tons of PG, are currently extant in the Gulf of Mexico region. The environmental and economic liabilities associated with PG stockpiling has prompted continuing research into alternative beneficial uses of this solid waste which will be protective of the public health. To investigate the efficacy of PG in the construction of artificial reefs, we conducted two preliminary studies which demonstrate that cement-consolidated PG may provide a suitable and safe substrate for artificial reef construction. The first, performed in the laboratory, examined the possibility of bioaccumulation of radium and six heavy metals over time when three levels (copepods, grass shrimp, and fishes) of an aquatic food chain experience both trophic and environmental exposure to PG. Other than higher radium levels in the experimental grass shrimp, little possible effect of PG exposure could be discerned. In all cases where increased metals concentrations were indicated within the experimental groups, roughly equivalent increases in metal concentrations also occurred in the control groups. The second, performed under natural conditions in four ¼-acre estuarine ponds, evaluated the effects of PG exposure on the community structures of marine meiofauna, macroinvertebrates, and fishes. Abundances of copepod species either were slightly increased in ponds with PG or were inconsistently affected. Diversity indices for macroinvertebrates and fishes showed modest but inconsistent variation among experimental and control ponds. Thus, no differences in community structure attributable to the presence of PG could be detected among benthic invertebrates, natant invertebrates, or fishes

Toxicity and bioaccumulation of TNT in marine fish in sediment exposures

The bioaccumulation potential and toxicity of 2, 4, 6-trinitrotoluene (TNT) spiked to sediment was evaluated in juvenile sheeps head minnows (JSHM, Cyprinodon variegatus) and adult freckled blennies (FB, Hypsoblennius ionthas). The JSHM were exposed for 4 days in the presence or absence of a mesh separating fish from sediment. FB were exposed to sediment for 7 days. During the 24-day storage period(4 °C), extensive transformation of spiked TNT occurred and concentrations are expressed as the sum of TNT, aminodinitrotoluenes and diaminonitrotoluenes (Sum TNT), on a dry weight basis. Sum TNT in the overlying water, not exchanged during exposure, increased gradually. Survival was high( ≥ 90%) for JSHM exposed to 7 mgkg-1 and FB exposed to up to 260 mgkg-1. All SHM died after 24-h exposure to 340 mgkg-1. Isolation from sediment did not significantly affect water concentrations or decrease bioaccumulation. Uptake from contact to sediment was likely negligible and bioaccumulation was from the overlying water. The feeding rate of FB exposed to 1700 μmol kg-1 sediment suspended in water for 24-h was significantly reduced by 50%

Response of the benthic food web to short- and long-term nutrient 1 enrichment in saltmarsh mudflats

Author Posting. © The Author(s), 2013. This is the author's version of the work. It is posted here by permission of Inter-Research for personal use, not for redistribution. The definitive version was published in Marine Ecology Progress Series 474 (2013): 27-41, doi:10.3354/meps10090.We examined the responses of biota at or near the base of the benthic food web to nutrient enrichment in salt marsh mudflats in Plum Island estuary (Massachusetts, USA). To simulate eutrophication, nitrate and phosphate loading rates were increased 10- to 15-fold in creeks fertilized for 2 mo (i.e. short-term enrichment) or 6 yr (chronic enrichment). We found that benthic invertebrate community structure was not altered by nutrient enrichment, although the abundance of epifaunal, but not infaunal, grazers increased. Short-term enrichment had no effect on the food web, but significant changes were detected with chronic enrichment. Grazing experiments with 15N-enriched bacteria and 13C-enriched benthic algae revealed higher per capita ingestion rates of benthic microalgae by nematodes, copepods and hydrobiid snails in the creek with chronic nutrient enrichment where isotope composition also indicated that algae increased in dietary importance. The fraction of bacterial biomass grazed was not affected by nutrient enrichment; however, the fraction of benthic algal biomass grazed increased by 235% with chronic enrichment. This higher grazing pressure was partly the result of dietary changes (increases in per capita feeding rate or a change in selection) but was mostly due to an increased abundance of the grazing consumer with the highest biomass, the snail Nassarius obsoletus. This increased top-down control partially masked the bottom-up effects of nutrient enrichment on algal biomass and helps explain the slow and inconsistent response of microalgal biomass to chronic nutrient enrichment previously observed in this estuary. Our research shows that eutrophication may subtly affect benthic food webs before large, sustained increases in algal biomass are observed.Pierre-Yves Pascal conducted this research while being supported by a 563 postdoctoral fellowship funded by the Department of Energy Office of Biological and 564 Environmental Research Award DE-FG02-05ER64070 and the Louisiana State University 565 College of Science. This material is based upon work supported by the National Science 566 Foundation under Grant Nos. 0213767 and 9726921

Saltmarsh plants, but not fertilizer, facilitate invertebrate recolonization after an oil spill

Foundation species contribute to the recovery of animal communities from disturbance by engineering, by improving habitat quality, and by regulating food availability. In a salt marsh impacted by the Deepwater Horizon oil spill, we tested the hypothesis that nutrient subsidies would enhance the positive effects of the foundation species Spartina alterniflora on the initial recolonization of benthic invertebrate communities (e.g., copepods, annelids, nematodes) by augmenting food (i.e., microalgae) availability. After two months, plantings of S.alterniflora significantly elevated the densities of the polychaete Capitella capitata, meiofauna-sized annelids, and total macroinfauna over unplanted plots. After 7months, the significant effect of plantings persisted for meiofauna-sized annelids, but not for C.capitata and total macroinfauna. Plantings had no effect on copepods (including Nannopus palustris, the dominant species), nematodes, or microalgal biomass for either month. Nutrient additions did not influence any taxon, despite initial increases in benthic microalgal biomass after 2months. We hypothesize that the structural effects of plants were important to early colonization, possibly by facilitating larval settlement or ameliorating temperature and desiccation stress. Our results emphasize the importance of re-establishing foundation species in oil-impacted sites to enhance recolonization of saltmarsh annelids, but suggest that recolonization is not promoted by the addition of nutrients