Reef fish demographics on Louisiana artificial reefs : the effects of reef size on biomass distribution and foraging dynamics

Understanding the role that habitat plays in the life history of reef-associated fishes is particularly significant given the dramatic increase in the number of artificial reefs deployed in coastal ecosystems over the past 50 years. In the Gulf of Mexico, the oil and gas industry has added a significant amount of structure to the Louisiana continental shelf, creating the largest de facto artificial reef deployment area in the world. Noting their usefulness as fish habitat, the Louisiana Artificial Reef Program was established to convert decommissioned platforms into artificial reefs. However, very little quantitative information exists on how these habitats affect the associated fish assemblage. The two objectives of this study were to examine high-resolution spatial and temporal distribution around two standing and two toppled platforms, and to examine the trophic ecology of common reef-associated fishes, such as red snapper (Lutjanus campechanus). Spatial distribution of fish biomass was examined using a multifrequency hydroacoustic approach to examine the extent of the area of influence around the two habitats and to examine diel changes in distribution. Standing platforms supported roughly two times higher biomass than toppled platforms, particularly in the upper water column at close ranges to the structures. Diel periodicity was evident, with higher biomass in the upper water column during the night and higher biomass in the lower water column during daylight hours. Diel periodicity was dependent on habitat and distance from the reef, breaking down at close range to standing platforms, likely a result of the light field emitted by working platforms. Trophic ecology was assessed with a combination of gut content and stable isotope analyses to examine both prey and sources of basal resources to the reef habitats. Results indicate that red snapper are opportunistic feeders, and that artificial reef structures do not provide a unique set of prey items, indicating that prey and basal resources are consistently sourced from the surrounding water column and soft bottom sediments. Additionally, no evidence of an area of prey depletion (feeding halo) was found around the two habitats, further indicating that prey is derived opportunistically from areas surrounding the reef structures

The effect of an inshore artificial reef on the community structure and feeding ecology of estuarine fishes in Barataria Bay, Louisiana

Recently we have begun to understand the importance of inshore hard-bottom substrate, including oyster reefs, to estuarine fish communities in the Gulf of Mexico, especially in the context of identifying Essential Fish Habitat (EFH). However, problems such as habitat loss, disease, overharvest, and failure to replace shell have severely decreased the amount of high-relief oyster reef habitat available to finfish. The purpose of this project was to establish an artificial high-relief mimic-oyster reef in Barataria Bay, Louisiana, and monitor its use by economically and ecologically important finfish, including spotted seatrout (Cynoscion nebulosus) and Atlantic croaker (Micropogonias undulatus). The finfish and invertebrate communities over the artificial reef site were compared to a mud bottom reference site, using two different gear types to sample the entire water column. I also examined site-specific trophic linkages by enumerating gut contents and performing stable isotope analyses of spotted seatrout, Atlantic croaker and bay anchovy (Anchoa mitchilli). There was no overall difference in the community structure between sites, though there was a seasonal difference in the numbers of individuals found at both sites. Species richness also varied by season, with highest number of species present in summer months. Results of the gut-content analysis showed that diets of spotted seatrout do not differ significantly between sites. Spotted seatrout consumed mostly fish and anchovies by number, and penaeid shrimp by weight. Stable isotope analysis indicated that while there were no overall differences in mean stable isotope values, the dietary breadth of spotted seatrout was greater over the artificial reef. In contrast, results indicated that there were significant differences in the diets Atlantic croaker between sites. Atlantic croaker diets consisted of mud crabs (Xanthidae) and other, unidentifiable crabs over the reef, and bivalves and fish over the reference site. Stable isotope analysis of Atlantic croaker indicates that overall dietary breadth was similar between sites, though 15N values were significantly higher over the artificial reef. Results of the stable isotope analysis for bay anchovy indicate that there was a greater dietary breath over the artificial reef

Spatio-temporal distribution of euphausiids: an important component to understanding ecosystem processes in the Gulf of Alaska and eastern Bering Sea

Abstract Euphausiids (principally Thysanoessa spp.) are found in high abundance in both the eastern Bering Sea (EBS) and the Gulf of Alaska (GOA). They are an important part of these cold-water coastal and pelagic ecosystems as a key prey item for many species, including marine mammals, seabirds, and fish, forming an ecological link between primary production and higher trophic levels. Acoustic-trawl (AT) survey methods provide a means of monitoring euphausiid abundance and distribution over a large spatial scale. Four years of AT and bottom-trawl survey data (2003, 2005, 2011, and 2013) were available from consistently sampled areas around Kodiak Island, including Shelikof Strait, Barnabas Trough, and Chiniak Trough. We identified euphausiid backscatter using relative frequency response and targeted trawling, and created an annual index of abundance for euphausiids. This index has broad application, including use in the stock assessments for GOA walleye pollock (Gadus chalcogrammus) and other species, as an ecosystem indicator, and to inform ecological research. We then used generalized additive models (GAMs) to examine the relationship between relative euphausiid abundance and potential predictors, including pollock abundance, temperature, bottom depth, and primary production. Model results were compared with an updated GAM of euphausiid abundance from the EBS to determine if the factors driving abundance and distribution were consistent between both systems. Temperature was not a strong predictor of euphausiid abundance in the GOA as in the EBS; warmer temperatures and lack of seasonal ice cover in the GOA may be a key difference between these ecosystems. Pollock abundance was significant in both the GOA and the EBS models, but was not a strongly negative predictor of euphausiid abundance in either system, a result not consistent with top-down control of euphausiid abundance

Multiple reassortment events in the evolutionary history of H1N1 influenza A virus since 1918

The H1N1 subtype of influenza A virus has caused substantial morbidity and mortality in humans, first documented in the global pandemic of 1918 and continuing to the present day. Despite this disease burden, the evolutionary history of the A/H1N1 virus is not well understood, particularly whether there is a virological basis for several notable epidemics of unusual severity in the 1940s and 1950s. Using a data set of 71 representative complete genome sequences sampled between 1918 and 2006, we show that segmental reassortment has played an important role in the genomic evolution of A/H1N1 since 1918. Specifically, we demonstrate that an A/H1N1 isolate from the 1947 epidemic acquired novel PB2 and HA genes through intra-subtype reassortment, which may explain the abrupt antigenic evolution of this virus. Similarly, the 1951 influenza epidemic may also have been associated with reassortant A/H1N1 viruses. Intra-subtype reassortment therefore appears to be a more important process in the evolution and epidemiology of H1N1 influenza A virus than previously realized

Mobile encounters:bus 5A as a cross-cultural meeting place

The paper explores modes of encounters in the everyday practice of bus travel. Particularly, it addresses cross-cultural encounters located in the tension between familiarity and difference, between inclusion and exclusion. The paper is located in contemporary thoughts, approaching public transport not only as a moving device but also as a social arena. Furthermore, the bus is simultaneously perceived as a public space, at once composite, contradictory and heterogeneous, and as a meeting place involving ‘Throwntogetherness’. The encounters analysed are bodily, emotional charged and outspoken meetings between passengers, with the socio-materiality of the bus and drivers as co-riders and gatekeepers

Stochastic Processes Are Key Determinants of Short-Term Evolution in Influenza A Virus

Understanding the evolutionary dynamics of influenza A virus is central to its surveillance and control. While immune-driven antigenic drift is a key determinant of viral evolution across epidemic seasons, the evolutionary processes shaping influenza virus diversity within seasons are less clear. Here we show with a phylogenetic analysis of 413 complete genomes of human H3N2 influenza A viruses collected between 1997 and 2005 from New York State, United States, that genetic diversity is both abundant and largely generated through the seasonal importation of multiple divergent clades of the same subtype. These clades cocirculated within New York State, allowing frequent reassortment and generating genome-wide diversity. However, relatively low levels of positive selection and genetic diversity were observed at amino acid sites considered important in antigenic drift. These results indicate that adaptive evolution occurs only sporadically in influenza A virus; rather, the stochastic processes of viral migration and clade reassortment play a vital role in shaping short-term evolutionary dynamics. Thus, predicting future patterns of influenza virus evolution for vaccine strain selection is inherently complex and requires intensive surveillance, whole-genome sequencing, and phenotypic analysis

Plant Species\u27 Origin Predicts Dominance and Response to Nutrient Enrichment and Herbivores in Global Grasslands

Exotic species dominate many communities; however the functional significance of species\u27 biogeographic origin remains highly contentious. This debate is fuelled in part by the lack of globally replicated, systematic data assessing the relationship between species provenance, function and response to perturbations. We examined the abundance of native and exotic plant species at 64 grasslands in 13 countries, and at a subset of the sites we experimentally tested native and exotic species responses to two fundamental drivers of invasion, mineral nutrient supplies and vertebrate herbivory. Exotic species are six times more likely to dominate communities than native species. Furthermore, while experimental nutrient addition increases the cover and richness of exotic species, nutrients decrease native diversity and cover. Native and exotic species also differ in their response to vertebrate consumer exclusion. These results suggest that species origin has functional significance, and that eutrophication will lead to increased exotic dominance in grasslands