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Oakes J.M.,Southern Cross University of Australia | Eyre B.D.,Southern Cross University of Australia | Ross D.J.,Tasmanian Aquaculture and Fisheries Institute
Environmental Science and Technology | Year: 2011

To determine the role of sediment denitrification in removing inputs of primary- (PE) and secondary-treated effluent (SE) from a pulp and paper mill (PPM), organic matter (OM) associated with PE (residual wood fiber) and SE (activated sludge biomass and phytoplankton) was added to estuarine intertidal sediments and denitrification rates were measured over 27 days. Labile sludge biomass and phytoplankton initially stimulated denitrification, including for pre-existing sediment N. After 2.5 d, however, denitrification was suppressed apparently due to microbial competition for N to process the refractory (high C:N) material remaining. Wood fiber suppressed denitrification throughout the experiment due to competition for N to process the refractory OM. Ultimate long-term denitrification suppression by phytoplankton is offset by initial enhanced denitrification rates. Although nutrient release during degradation of sludge biomass and wood fiber may stimulate phytoplankton production, N equivalent to 127% of the expected daily phytoplankton load was denitrified within 24 h, allowing for permanent removal of PPM-derived N. Compared to primary treatment, secondary treatment of PPM effluent has greater potential for N removal. © 2011 American Chemical Society.

Oakes J.M.,Southern Cross University of Australia | Eyre B.D.,Southern Cross University of Australia | Ross D.J.,Tasmanian Aquaculture and Fisheries Institute | Turner S.D.,Southern Cross University of Australia
Environmental Science and Technology | Year: 2010

Stable isotope analysis of a novel combination of carbon and nitrogen pools traced inputs and processing of primary-treated (PE) and secondary-treated effluent (SE) from a paper and pulp mill (PPM) in a temperate Australian estuary. Distinct carbon stable isotope ratios of dissolved organic carbon (DOC) near the PPM outfall indicated large PE and reduced SE inputs of DOC. DOC was remineralized to dissolved inorganic carbon regardless of season, but rates were lower in winter. PE discharge in winter elevated DOC concentrations along much of the estuary. Distinct stable isotope ratios confirmed particulate organic matter (POM) input from PE and SE to the water column and into the sediment. This was relatively localized, indicating rapid POM settlement regardless of season. SE discharge increased nutrient inputs and enhanced algal productivity, particularly in summer when chlorophyll-a concentrations were elevated throughout the estuary. SE discharge reduced pCO2 from levels associated with PE discharge. However, the estuary remained heterotrophic as subsequent respiration or decomposition of algal material offset reductions in PPM organic matter input. The influence of the PPM was apparent throughout the estuary, demonstrating the ability of anthropogenic inputs, and changes to these, to affect ecosystem functioning. © 2010 American Chemical Society.

Kawaguchi S.,Australian Antarctic Division | King R.,Australian Antarctic Division | Meijers R.,University of Tasmania | Osborn J.E.,University of Tasmania | And 3 more authors.
Deep-Sea Research Part II: Topical Studies in Oceanography | Year: 2010

Schooling behaviour of Antarctic krill was induced repeatedly over a period of one year in the Australian Antarctic Division research aquarium. The details of the laboratory setup suitable for krill to school are described. Light intensity and food condition were found to affect krill swimming patterns and schooling behaviour. Krill swam in polarised groups and responded as a group to objects that produced sharp contrasts but not to less distinct objects. Schools broke up when they encountered dense phytoplankton patches, and aggregated more tightly when kept with a white featureless background. The diel nature of school formation was observed under simulated natural light conditions with stronger and tighter schools during daytime and no obvious schooling behaviour during night. These behavioural patterns are further discussed in terms of their costs and benefits of feeding and predation risk, in conjunction with the diel vertical migration behaviour of krill. Crown Copyright © 2009.

Young J.W.,CSIRO | Lansdell M.J.,CSIRO | Campbell R.A.,CSIRO | Cooper S.P.,CSIRO | And 2 more authors.
Marine Biology | Year: 2010

We examined the feeding ecology and niche segregation of the ten most abundant fish species caught by longline operations off eastern Australia between 1992 and 2006. Diets of 3,562 individuals were examined. Hook timer data were collected from a further 328 fish to examine feeding behaviour in relation to depth and time of day. Prey biomass was significantly related to predator species, predator length and year and latitude of capture. Although the fish examined fed on a mix of fish, squid and crustacea, fish dominated the diet of all species except small albacore (Thunnus alalunga) which fed mainly on crustacea and large swordfish (Xiphias gladius) and albacore which fed mainly on squid. Cannibalism was observed in lancetfish (Alepisaurus spp.). Multidimensional scaling identified three species groups based on their diet composition. One group consisted of yellowfin tuna (T. albacares), striped marlin (Tetrapturus audax) and dolphinfish (Coryphaena hippurus); a second group consisted of bigeye tuna (T. obesus), swordfish and albacore; and a third consisted of southern bluefin tuna (T. maccoyii) and blue shark (Prionace glauca). Of note was the separation of mako shark (Isurus oxyrhynchus) and lancetfish from all other predators. Prey length generally increased with increasing predator length although even large predators fed on a wide range of prey lengths including very small prey. Overall, differences in prey type and size, feeding times and depths were noted across the range of species examined to the extent that predators with overlapping prey, either in type or size, fed at different times of the diel period or at different depths. Taken together these data provide evidence for feeding niche segregation across the range of oceanic top predators examined. © 2010 Springer-Verlag.

Keeley N.B.,Cawthron Institute | Keeley N.B.,University of Tasmania | MacLeod C.K.,University of Tasmania | MacLeod C.K.,Tasmanian Aquaculture and Fisheries Institute | Forrest B.M.,Cawthron Institute
Ecological Indicators | Year: 2012

Many benthic quality indices rely on categorising impacts by assigning species to ecological-groups (EGs) that reflect their tolerance to pollution. This is usually based on best professional judgement (BPJ) by experts with access to relevant ecological and taxonomic information. However, international applicability of such indices is restricted in areas where the species taxonomy, biology and response to pollution are poorly understood. In this study we describe an approach that enables objective allocation of EGs in situations where species information is limited. This approach utilised BPJ to categorise the environmental condition of benthic habitats around fish farms in New Zealand in relation to defined enrichment stages (ESs). Quantile regression was then used to model distributions of select taxa. The experts assigned ES scores from 1 to 7, for stations that ranged from relatively natural to excessively enriched (i.e. near-azoic), respectively, with judgements based on a suite of quantitative and qualitative indicators of enrichment, but without reference to detailed species information. The individual BPJ estimates were highly correlated, with minimal bias, indicating good agreement among the experts. Forty key indicator taxa were identified and quantile regression models based on ES (derived as a continuous explanatory variable) were fitted for 34. Abundances of the same taxa were also modelled in response to a more traditional enrichment indicator (organic content, %OM) for comparison with the BPJ technique. The regression approach characterised enrichment responses and objectively identified both the upper and lower tolerance limits of a range of taxa according to their ES and %OM. The models discriminated a number of key indicator taxa, including several that were responsive to low-level changes in ES, but not necessarily %OM. There was reasonable agreement (59%) between EGs derived using the regression approach and those defined using the AMBI database (one of the most commonly applied benthic quality indices). Moreover, the regression method allowed the classification of 10 additional taxa for which our ecological understanding was limited. A key outcome of this study was the acknowledgement that EG characterisations for species need to be regionally validated, no matter how well defined they might appear to be. The combined BPJ/regression analysis approach described provides a valid means of both assigning and validating EG classifications, which will be particularly useful in situations where the taxa are poorly defined, and will enable existing biotic indices to be more broadly applied and interpreted. © 2011 Elsevier Ltd.

Stuart-Smith R.D.,Tasmanian Aquaculture and Fisheries Institute | Barrett N.S.,Tasmanian Aquaculture and Fisheries Institute | Stevenson D.G.,Tasmanian Aquaculture and Fisheries Institute | Edgar G.J.,Tasmanian Aquaculture and Fisheries Institute
Global Change Biology | Year: 2010

Despite increasing scientific and public concerns on the potential impacts of global ocean warming on marine biodiversity, very few empirical data on community-level responses to rising water temperatures are available other than for coral reefs. This study describes changes in temperate subtidal reef communities over decadal and regional scales in a location that has undergone considerable warming in recent decades and is forecast to be a 'hotspot' for future warming. Plant and animal communities at 136 rocky reef sites around Tasmania (south-east Australia) were censused between 1992 and 1995, and again in 2006 and 2007. Despite evidence of major ecological changes before the period of study, reef communities appeared to remain relatively stable over the past decade. Multivariate analyses and univariate metrics of biotic communities revealed few changes with time, although some species-level responses could be interpreted as symptomatic of ocean warming. These included fishes detected in Tasmania only in recent surveys and several species with warmer water affinities that appeared to extend their distributions further south. The most statistically significant changes observed in species abundances, however, were not related to their biogeographical affinities. The majority of species with changing abundance possessed lower to mid-range abundances rather than being common, raising questions for biodiversity monitoring and management. We suggest that our study encompassed a relatively stable period following more abrupt change, and that commu- nity responses to ocean warming may follow nonlinear, step-like trajectories. © 2009 Blackwell Publishing Ltd.

Swadling K.M.,Tasmanian Aquaculture and Fisheries Institute | Kawaguchi S.,Australian Antarctic Division | Hosie G.W.,Australian Antarctic Division
Deep-Sea Research Part II: Topical Studies in Oceanography | Year: 2010

The distribution of mesozooplankton, based on the catch by a RMT1 net, in the upper 200 m of the South Western Indian Ocean sector (30°E-80°E) of the Southern Ocean was examined during the large-scale BROKE-West survey in summer 2006. Multivariate analyses revealed four groups of zooplankton that could be broadly linked to oceanographic features. The first group, occurring south of the southern boundary of the Antarctic Circumpolar Current (sbACC) and west of 40°E, was associated with waters from the eastern limb of the Weddell Gyre. The group was typified by moderate abundance (mean: 11,251 ind. 1000 m-3) and included foraminiferans, appendicularians and small copepods. Group 2 was composed of stations found in the deeper, warmer waters lying between the sbACC and the southern ACC front (sACCf), along with a few stations north of the sACCf. Sites in this group exhibited the highest mean zooplankton abundance (81,750 ind. 1000 m-3) and comprised large numbers of small copepods and appendicularians. Sites in group 3 fell south of the sbACC, were situated east of 50°E, and generally located near the Antarctic slope current (ASC), a strong and narrow jet of westward flowing water. Typical species for this group included Euphausia crystallorophias, Fritillaria spp. and Metridia gerlachei. Finally, group 4 represented neritic sites in the far southwestern corner of the survey region. Abundances were lowest (mean: 2588 ind. 1000 m-3) and the assemblage was dominated by E. crystallorophias, Neogloboquadrina pachyderma and Fritillaria spp. The four groups differed more by abundance than by composition. The suite of environmental variables that best correlated with patterns in the species data included chlorophyll a concentration, proximity to the ASC and length of time without an ice cover, all features which indicated that large scale oceanographic processes were underpinning the patterns in mesozooplankton distribution. © 2009 Elsevier Ltd.

Young J.W.,CSIRO | Guest M.A.,Tasmanian Aquaculture and Fisheries Institute | Lansdell M.,CSIRO | Phleger C.F.,CSIRO | And 3 more authors.
Progress in Oceanography | Year: 2010

Signature lipid and fatty acid analysis were used to discriminate the diet of swordfish (Xiphias gladius, orbital fork length: 60-203 cm) from waters off eastern Australia. The fatty acid (FA) composition of a range of known prey (squid, myctophids, and other fishes) of swordfish, taken from stomach samples and from net tows, was compared with that of the white muscle tissue (WMT) of swordfish from the same region. Swordfish muscle was lipid rich (average 24-42% dry weight), as was the skeleton (28-41%). The robustness of the approach was also tested by comparison against a key squid prey species that was collected and stored using different protocols: (i) fresh frozen, (ii) fresh frozen, then thawed, and (iii) stomach content collection. The FA profiles were generally similar, with the ratio of docosahexaenoic acid (DHA) and palmitic acid (16:0) in particular showing no significant difference. Major fatty acids in swordfish WMT were 18:1ω9c, 16:0, 22:6ω3, and 18:0. Multidimensional scaling showed that the swordfish WMT grouped closely with small fish prey including myctophids, and not with squid. Squid contained markedly higher 22:6ω3 than swordfish. Individual prey species of the myctophidae could also be separated by the same technique. These results were supported by traditional stomach content analyses (SCA) that showed fish were the dominant prey for small swordfish sampled from southern waters whereas squid were the main prey in more northern waters, matching the FA patterns we found for the two regions. We propose that where general diet patterns are established, signature FA analysis has good potential to compliment or in some cases, replace temporal and spatial monitoring of trophic pathways for swordfish and other marine species. © 2010.

Abrantes K.G.,James Cook University | Abrantes K.G.,Catholic University of Leuven | Barnett A.,Tasmanian Aquaculture and Fisheries Institute
Marine Ecology Progress Series | Year: 2011

Intrapopulation differences in diet and/or movement are important for understanding the role mobile predators play in different systems. However, ecological studies traditionally overlook individual differences. δ13C and δ15N were used in conjunction with diet and movement information to identify intrapopulation differences in diet and movement patterns of the apex predator broadnose sevengill shark Notorynchus cepedianus in southeast Tasmania. Sevengill samples from 3 inshore and 3 offshore sites were collected, and δ13C and δ15N compared between sites, sizes and sexes. Individuals captured offshore had lower δ15N than those captured inshore, indicating some degree of spatial segregation. Sevengills also had variable δ13C and δ15N within coastal habitats, suggesting intrapopulation differences in diet or migration schedules. In comparison to their main prey, most individuals had δ15N lower than expected for a top predator, also suggesting that they do not reside permanently in these areas, as their tissue was not in isotopic equilibrium with their known prey. This is in agreement with tracking data that showed seasonal use of coastal areas, with most animals leaving for the colder months but returning the following year. There was also a group of females with relatively high δ13C that suggests greater association to coastal habitats, again in agreement with tracking data, as some tagged females remained in the coastal areas over winter. Overall, together with diet and tracking information, results indicate that there are differences in movement and possibly diet in this sevengill population. This multimethods approach allowed a better understanding of sevengill ecology than the use of any one of the techniques alone. © Inter-Research 2011.

Marzloff M.P.,Institute for Marine and Antarctic Studies | Marzloff M.P.,CSIRO | Marzloff M.P.,Tasmanian Aquaculture and Fisheries Institute | Dambacher J.M.,CSIRO | And 3 more authors.
Ecological Modelling | Year: 2011

Demonstrating and predicting the existence of alternative states in natural communities remains a challenge for ecologists and is essential for resource managers. Positive feedback is often presented as central in maintaining alternative ecosystem states, but no formal approach relates this part of theory to real world applications. Through qualitative modelling of community response to long-term perturbations, we define generic mechanistic links between positive feedback and the occurrence of alternative states. Positive feedback diminishes a system's overall resistance to change, and can create and maintain correlations in the relative abundance of variables that coincide with alternative states. Through specific models of the dynamics of Tasmanian rocky-reef communities, which are affected by climate and fishing and persist within alternative states, we demonstrate the ability of our theoretical framework to predict alternative states in ecosystems and inform management intervention. A qualitative knowledge of community structure permits a thorough analysis of system feedback and an assessment of the potential for an ecosystem to exhibit alternative states. We illustrate the usefulness of the approach to inform management priorities, and to focus monitoring and field research on the key drivers of ecosystem dynamics. © 2011 Elsevier B.V.

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