Seasonal and interannual variability in physical processes, nutrient cycling and the structure of the food chain in Tasmanian shelf waters

Harris, Graham P.; Griffiths, F. Brian; Clementson, Lesley A.; Lyne, Vincent; Doe, Helen

doi:10.1093/oxfordjournals.plankt.a042363

Cited by 13 publications

(2 citation statements)

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“…They also provide contextualization to reports of the poleward range expansion of macroscopic organisms in the region that have been attributed in part to the increasing strength of the EAC (Armbrecht et al, 2015;Figueira & Booth, 2010;Harris, Griffiths, Clementson, Lyne, & Van der Doe, 1991;Johnson et al, 2011;Kingsbury et al, 2020;Last et al, 2011;Ling et al, 2009). These shifts have had substantial implications for the ecology of temperate waters in the region (Vergés et al, 2014), resulting in cascading losses of taxonomic diversity (Johnson et al, 2011;Ling et al, 2009), and the generation of new communities comprising sympatric tropical and temperate species (Kingsbury et al, 2020).…”

Section: Expanding Eac-driven Tropicalizationmentioning

confidence: 78%

Microbial tropicalization driven by a strengthening western ocean boundary current

Messer

Ostrowski

Doblin

et al. 2020

Global Change Biology

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Western boundary currents (WBCs) redistribute heat and oligotrophic seawater from the tropics to temperate latitudes, with several displaying substantial climate change‐driven intensification over the last century. Strengthening WBCs have been implicated in the poleward range expansion of marine macroflora and fauna, however, the impacts on the structure and function of temperate microbial communities are largely unknown. Here we show that the major subtropical WBC of the South Pacific Ocean, the East Australian Current (EAC), transports microbial assemblages that maintain tropical and oligotrophic (k‐strategist) signatures, to seasonally displace more copiotrophic (r‐strategist) temperate microbial populations within temperate latitudes of the Tasman Sea. We identified specific characteristics of EAC microbial assemblages compared with non‐EAC assemblages, including strain transitions within the SAR11 clade, enrichment of Prochlorococcus, predicted smaller genome sizes and shifts in the importance of several functional genes, including those associated with cyanobacterial photosynthesis, secondary metabolism and fatty acid and lipid transport. At a temperate time‐series site in the Tasman Sea, we observed significant reductions in standing stocks of total carbon and chlorophyll a, and a shift towards smaller phytoplankton and carnivorous copepods, associated with the seasonal impact of the EAC microbial assemblage. In light of the substantial shifts in microbial assemblage structure and function associated with the EAC, we conclude that climate‐driven expansions of WBCs will expand the range of tropical oligotrophic microbes, and potentially profoundly impact the trophic status of temperate waters.

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Section: Expanding Eac-driven Tropicalizationmentioning

confidence: 78%

Microbial tropicalization driven by a strengthening western ocean boundary current

Messer

Ostrowski

Doblin

et al. 2020

Global Change Biology

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“…The impacts of the intensification of the EAC southern extension on coastal systems are already evident and include prolonged marine heatwaves (Oliver et al, 2017;Schaeffer et al, 2017;Huang et al, 2021), modification of nutrient loading regimes (Harris et al, 1987;Harris et al, 1991) migration of typically subtropical species poleward (Edyvane, 2003;Pittock, 2003;Thresher et al, 2003;Vergeś et al, 2014;Niella et al, 2021) and shifts in species assemblages, the distributions of pelagic fish and planktic species, and trophic interactions (Carroll et al, 2016;Carroll et al, 2017;Hobday et al, 2011;Johnson et al, 2011;Kelly et al, 2016;Larsson et al, 2018;Thompson et al, 2009) that are projected to continue in coming decades (Cetina-Heredia et al, 2015). While many ecological patterns have been investigated in the context of EAC variability via correlations with temperature and current velocity, there has been little work investigating how EAC variability (or western boundary current variability more broadly) influences seascape characteristics over multiple spatiotemporal scales simultaneously, including how relationships between geostrophic and ageostrophic processes link offshore and coastal dynamics, and impact biological activity.…”

Section: Introductionmentioning

confidence: 99%

Coastal seascape variability in the intensifying East Australian Current Southern Extension

et al. 2022

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Coastal pelagic ecosystems are highly variable in space and time, with environmental conditions and the distribution of biomass being driven by complex processes operating at multiple scales. The emergent properties of these processes and their interactive effects result in complex and dynamic environmental mosaics referred to as “seascapes”. Mechanisms that link large-scale oceanographic processes and ecological variability in coastal environments remain poorly understood, despite their importance for predicting how ecosystems will respond to climate change. Here we assessed seascape variability along the path of the rapidly intensifying East Australian Current (EAC) Southern Extension in southeast Australia, a hotspot of ocean warming and ecosystem tropicalisation. Using satellite and in situ measures of temperature, salinity and current velocity coupled with contemporaneous measurements of pelagic biomass distribution from nine boat-based active acoustic surveys in five consecutive years, we investigated relationships between the physical environment and the distribution of pelagic biomass (zooplankton and fish) at multiple timescales. Survey periods were characterised by high variability in oceanographic conditions, with variation in coastal conditions influenced by meso-to-large scale processes occurring offshore, including the position and strength of eddies. Intra-annual variability was often of a similar or greater magnitude to inter-annual variability, suggesting highly dynamic conditions with important variation occurring at scales of days to weeks. Two seascape categories were identified being characterised by (A) warmer, less saline water and (B) cooler, more saline water, with the former indicating greater influence of the EAC on coastal processes. Warmer waters were also associated with fewer, deeper and less dense biological aggregations. As the EAC continues to warm and penetrate further south, it is likely that this will have substantial effects on biological activity in coastal pelagic ecosystems, including a potential reduction in the accessibility of prey aggregations to surface-feeding predators and to fisheries. These results highlight the import role of offshore oceanographic processes in driving coastal seascape variability and biological activity in a region undergoing rapid oceanic warming and ecological change.

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Spatial and temporal variation in the diet of a high trophic level predator, the Australian fur seal ( Arctocephalus pusillus doriferus )

Hume¹,

Hindell

Pemberton

et al. 2004

Marine Biology

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Seasonal and interannual variability in physical processes, nutrient cycling and the structure of the food chain in Tasmanian shelf waters

Cited by 13 publications

References 0 publications

Microbial tropicalization driven by a strengthening western ocean boundary current

Microbial tropicalization driven by a strengthening western ocean boundary current

Coastal seascape variability in the intensifying East Australian Current Southern Extension

Spatial and temporal variation in the diet of a high trophic level predator, the Australian fur seal ( Arctocephalus pusillus doriferus )

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