ALBERT

Description: Tauranga Harbour, New Zealand's largest barrier-enclosed coastal lagoon, comprises two sub-basins with separate catchments, inlets and tidal channel systems. This study sets out to assess and investigate the sediment dispersal system of Tauranga Harbour using standard environmental magnetic and sedimentological methods. Compilations of rock magnetic and grain size data of surficial sediments collected from inflowing rivers, various estuarine environments (estuaries, tidal flats and tidal channels) and the adjacent nearshore mirror the net and differential sediment fluxes into and through the two sub-basins of this lagoon. For all studied depositional environments, the magnetogranulometric ratios SIRM/k and ARM/k are positively correlated with magnetic mineral content (SIRM, ARM, X) in the sense that larger magnetic particles are associated with higher magnetic enrichment. Grain-size analyses show that magnetic enrichment during particle transport and deposition can result from grain-size as well as from grain-density fractionation. The periodically changing accumulation/erosion conditions provide for a selective retention of specific grain sizes and an enhancement of the heavier magnetic mineral particles. Magnetic crystal size and clastic grain size correlate poorly over the whole study area, but group within similar depositional environments. Coarser magnetic and clastic grain sizes and higher magnetite enrichment in the southern sub-basin can be reconciled with episodic flood runoff of the Wairoa River and a much larger, artificially deepened southern tidal inlet which likely enables higher tidal current velocities. Our approach of combining magnetic and clastic grain-size could be successfully implemented to establish a conceptual model of sediment dynamics and gravitational sorting within Tauranga Harbour.

Description: Benthic communities in Long Island Sound have experienced over 150 years of eutrophication and commercial shellfishing. We established an ecological baseline using a combination of live, dead, archaeological, and fossil mollusk material to investigate the impacts of these stressors on the molluscan community. We expected ecological change would increase with nutrient loading and eutrophication-induced hypoxia west towards New York City. Instead, crushing predation on bivalves has been suppressed below pre-anthropogenic baseline levels throughout the Sound, even in the well oxygenated east. Taxonomic similarity, rank order abundance, and drilling frequency are more strongly controlled by commercial fishing pressure than by declines in water quality. The absence of a clear relationship between eutrophication-hypoxia and ecological change questions the effectiveness of nitrogen reduction alone as a restoration strategy. Long Island Sound fossils revealed a relatively ancient loss of mollusks associated with seagrass and oyster habitats that predates death assemblage deposition and underscores the need for older material to reveal the shifting baseline. The interactive nature of multiple stressors means that overfishing may have dampened the response of communities in the Sound to eutrophication or inhibited their ability to recover. The unexpected role of hypoxic areas protected from commercial fishing as refuges highlights the utility of no-take marine preserves in eutrophied estuaries worldwide.

Description: Aim To quantify the influence of a suite of landscape, abiotic, biotic, and host-level variables on ranavirus disease dynamics in amphibian assemblages at two biological levels (site and host-level). Location Wetlands within the East Bay region of California, USA. Methods We used competing models, multimodel inference, and variance partitioning to examine the influence of 16 landscape and environmental factors on patterns in site-level ranavirus presence and host-level ranavirus infection in 76 wetlands and 1,377 amphibian hosts representing five species. Results The landscape factor explained more variation than any other factors in site-level ranavirus presence, but biotic and host-level factors explained more variation in host-level ranavirus infection. At both the site- and host-level, the probability of ranavirus presence correlated negatively with distance to nearest ranavirus-positive wetland. At the site-level, ranavirus presence was associated positively with taxonomic richness. However, infection prevalence within the amphibian population correlated negatively with vertebrate richness. Finally, amphibian host species differed in their likelihood of ranavirus infection: American Bullfrogs had the weakest association with infection while Western Toads had the strongest. After accounting for host species effects, hosts with greater snout-vent length had a lower probability of infection. Main conclusions Strong spatial influences at both biological levels suggest that mobile taxa (e.g., adult amphibians, birds, reptiles) may facilitate the movement of ranavirus among hosts and across the landscape. Higher taxonomic richness at sites may provide more opportunities for colonization or the presence of reservoir hosts that may influence ranavirus presence. Higher host richness correlating with higher ranavirus infection is suggestive of a dilution effect that has been observed for other amphibian disease systems and warrants further investigation. Our study demonstrates that an array of landscape, environmental, and host-level factors were associated with ranavirus epidemiology and illustrates that their importance varies with biological level.