http://hdl.handle.net/2440/10824 2020-02-27T11:55:05Z http://hdl.handle.net/2440/123449 Title: Interspecific interactions, movement patterns and habitat use in a diverse coastal shark assemblage Author: Heupel, M.; Munroe, S.; Lédée, E.; Chin, A.; Simpfendorfer, C. Abstract: Sharks are a highly diverse predatory taxon and are regularly found in large, potentially competitive, assemblages. However, the mechanisms that enable long-term coexistence and factors that drive complementary movement are poorly understood. As interspecific interactions can have a large influence on survival and trophic linkages, research on shark assemblages could substantially increase our understanding of marine community dynamics. In this study, we used passive acoustic telemetry to compare the activity space size, spatial overlap and habitat use patterns of six co-occurring shark species from the same family in a tropical nearshore embayment. Our results indicated that all sizes of Rhizoprionodon taylori (a small-bodied, highly productive species) used significantly larger amounts of space (e.g., mean 95% KUD = 85.9 km2) than juveniles of large-bodied, less productive species (e.g., Carcharhinus amboinensis; 62.3 km2) that use nearshore areas as nursery areas. Most large, less productive species appeared risk averse by using less space, while the smaller more productive species took greater risk by roaming broadly. These movement strategies are likely a means of avoiding predation or gaining access to new or additional resources. Spatial overlap patterns varied substantially between species with overlap in core use areas ranging from 1.2 to 27.6%, but were consistent over time. Most species exhibited low spatial overlap, suggesting spatial partitioning to reduce interspecific competition. While a few species exhibited a high degree of spatial overlap (up to 60% of activity space extent), dietary diversity may reduce competition to support co-occurrence. These data suggest that complex interactions occur in communal nurseries in nearshore waters where species are in direct competition for resources at vulnerable life stages. 2019-01-01T00:00:00Z http://hdl.handle.net/2440/123409 Title: Population-specific shifts in viral and microbial abundance within a cryptic upwelling Author: Paterson, J.; Nayar, S.; Mitchell, J.; Seuront, L. Abstract: Coastal upwelling systems play an essential role in bringing cold and nutrient-rich water into the euphotic zone, hence enhancing the biological productivity of the world's oceans. We describe a “cryptic” upwelling occurring in South Australian waters, in which cold upwelled waters do not reach surface waters and do not exhibit a sea surface temperature (SST) signature. Due to the wide continental shelf (ca. 100 km), upwelled waters form a sub-surface cold water pool and are forced north-west after a secondary event. Using flow cytometry we investigated the abundance and composition of viruses, heterotrophic bacteria and pico-phytoplankton within upwelling affected and unaffected waters. Our results identified the presence of upwelled waters at and below the Deep-Chlorophyll Maximum (DCM), where water temperature was at least 4 °C colder than surface waters. In contrast to previous studies, no significant differences were observed between upwelled and non-upwelled waters for most individual viral, bacterial and pico-phytoplankton sub-groups. However, one viral, one bacterial and two pico-phytoplankton sub-groups were significantly more abundant at the DCM. This indicates the presence of depth- and population-specific shifts in abundance and potential niche partitioning of these cytometrically-defined sub-groups that may be related to their host organisms and/or resource availability. 2013-01-01T00:00:00Z http://hdl.handle.net/2440/123345 Title: A benthic bioindicator reveals distinct land and ocean–based influences in an urbanized coastal embayment Author: Munroe, S.; Coates-Marnane, J.; Burford, M.; Fry, B. Abstract: Biogeochemical maps of coastal regions can be used to identify important influences and inputs that define nearshore environments and biota. Biogeochemical tracers can also track animal movement and their diet, monitor human coastal development, and evaluate the condition of habitats and species. However, the beneficial applications of spatial biogeochemical analysis are hindered by a limited understanding of how tracer distribution is affected by different land and ocean–based influences. To help address these knowledge gaps, we determined the spatial trends of three stable isotopes (δ13C-carbon, δ15N-nitrogen, δ34S-sulfur) and 13 major and trace elements in an urbanized coastal embayment (Moreton Bay, Australia), as incorporated into the muscle tissue of a marine consumer, the eastern king prawn Melicertus plebejus. Results were used to identify unique biochemical regions within the bay and to discuss how spatial patterns in tracers could be used to indicate the relative importance of catchment, urban and offshore drivers in coastal bays. Discriminant analysis identified seven biogeochemical regions that were likely distinguished by variation in catchment, urban, and offshore input, and habitat type. δ13C and δ15N patterns suggested nearshore areas could be distinguished by increased sediment resuspension and higher wastewater inputs from catchments. High inshore lead (Pb) and copper (Cu) concentrations were likely the result of urban input. Arsenic (As) and cadmium (Cd) increased further from shore. This trend implied oceanic influences were a significant control over As and Cd bioavailability. Cobalt (Co) and rare earths were also used to differentiate some nearshore areas, but incongruent distribution patterns in Co suggested it may be less reliable. Overall, results indicated that δ15N, δ13C, Cd, Cu, Pb and rare earth elements were the most reliable tracers to differentiate nearshore and offshore environments, and catchment–based effects. We encourage future studies to consider using a similar multivariate approach in coastal spatial analysis, and to include unrelated tracers that reflect distinct coastal influences. Description: Published: October 11, 2018 2018-01-01T00:00:00Z http://hdl.handle.net/2440/123344 Title: A global perspective on the trophic geography of sharks Author: Bird, C.S.; Veríssimo, A.; Magozzi, S.; Abrantes, K.G.; Aguilar, A.; Al-Reasi, H.; Barnett, A.; Bethea, D.M.; Biais, G.; Borrell, A.; Bouchoucha, M.; Boyle, M.; Brooks, E.J.; Brunnschweiler, J.; Bustamante, P.; Carlisle, A.; Catarino, D.; Caut, S.; Cherel, Y.; Chouvelon, T.; et al. Abstract: Sharks are a diverse group of mobile predators that forage across varied spatial scales and have the potential to influence food web dynamics. The ecological consequences of recent declines in shark biomass may extend across broader geographic ranges if shark taxa display common behavioural traits. By tracking the original site of photosynthetic fixation of carbon atoms that were ultimately assimilated into muscle tissues of 5,394 sharks from 114 species, we identify globally consistent biogeographic traits in trophic interactions between sharks found in different habitats. We show that populations of shelf-dwelling sharks derive a substantial proportion of their carbon from regional pelagic sources, but contain individuals that forage within additional isotopically diverse local food webs, such as those supported by terrestrial plant sources, benthic production and macrophytes. In contrast, oceanic sharks seem to use carbon derived from between 30° and 50° of latitude. Global-scale compilations of stable isotope data combined with biogeochemical modelling generate hypotheses regarding animal behaviours that can be tested with other methodological approaches. 2018-01-01T00:00:00Z