S. Duggan

Tropical Marginal Seas: Priority Regions for Managing Marine Biodiversity and Ecosystem Function

Tropical marginal seas (TMSs) are natural subregions of tropical oceans containing biodiverse ecosystems with conspicuous, valued, and vulnerable biodiversity assets. They are focal points for global marine conservation because they occur in regions where human populations are rapidly expanding. Our review of 11 TMSs focuses on three key ecosystems-coral reefs and emergent atolls, deep benthic systems, and pelagic biomes-and synthesizes, illustrates, and contrasts knowledge of biodiversity, ecosystem function, interaction between adjacent habitats, and anthropogenic pressures. TMSs vary in the extent that they have been subject to human influence-from the nearly pristine Coral Sea to the heavily exploited South China and Caribbean Seas-but we predict that they will all be similarly complex to manage because most span multiple national jurisdictions. We conclude that developing a structured process to identify ecologically and biologically significant areas that uses a set of globally agreed criteria is a tractable first step toward effective multinational and transboundary ecosystem management of TMSs.

Seacage aquaculture in a World Heritage Area: the environmental footprint of a Barramundi farm in tropical Australia.

The fate of aquaculture wastes from a seacage farm within a pristine mangrove environment was studied. Seasonal and tidal differences were most important in determining water quality within receiving waters and obscured any nutrient enrichment effect by the farm. Farm wastes added significantly to the N budget status of the creek system, but overall water quality conformed to Queensland EPA Water Quality standards. Mangrove trees throughout the creek system contained (15)N signatures traceable to aquaculture feeds, but the footprint of the farm itself was best indicated by the ratio of Zn:Li in sediments. The creek became hypoxic (<2 mgl(-1)) during wet season low tides. Consequently, we recommended monitoring of water-column oxygen concentrations to warn of hypoxic conditions threatening to fish health, as well as Zn:Li ratios in sediment accumulation zones to determine the area of influence of the farm.

Depth structuring of pelagic copepod biodiversity in waters adjacent to an Eastern Indian Ocean coral reef

We compared pelagic copepod communities at three (400+ m) stations adjacent to Scott Reef (14°S), a shelf-break reef in Australias Indian Ocean territory, with those within the shallow (c.50 m) atoll lagoon. The metazooplankton assemblage sampled by our 100-μm multinet system was dominated by small (< 1.0 mm) copepods. We identified over 220 copepod species, belonging to five of the nine orders. Of these, 68 (31%) are new records for Australian waters and at least 14 are likely to be undescribed. Redundancy analysis indicated that depth stratum was the most important determinant of community structure: distinct communities were associated with the epipelagic (within which the atoll lagoon community was further distinguished by reef-associated copepods), the chlorophyll maximum/thermocline, the upper mesopelagic and the hyper-benthos. The family Oncaeidae was highly speciose (> 52 taxa) and progressively more important with increasing depth.

Determinants of pelagic metabolism in the Timor Sea during the inter-monsoon period

The Timor Sea is a major conduit of the Indonesian Throughflow characterised by large internal waves and tides. To ascertain whether these result in high pelagic productivity, we conducted experiments to determine the metabolic balance between net community production (NCP) and community respiration (CR) on the Sahul Shelf, the Sahul Shoals and the Yampi Shelf, an area of active hydrocarbon seeps. The barrier to vertical mixing of subthermocline nutrients represented by the halocline allowed new production to dominate in March 2004, whereas production in June 2005 depended on recycled nutrients. CR was correlated with dissolved organic carbon (DOC) in 2004, but with chlorophyll in 2005, suggesting that respiration was dominated by microheterotrophs in 2004 but by autotrophs in 2005. Overall, area-specific CR averaged 120 ± 92 (s.d.), 101 ± 52 and 61 ± 6 mmol O2 m–2 day–1, NCP averaged 109 ± 85 (s.d.), 32 ± 41 and 57 ± 10 mmol O2 m–2 day–1, and average gross primary production (= CR+NCP) : R ratios were 1.9, 1.4 and 1.9 on the shelf, at the Sahul Shoals and the Yampi Shelf, respectively. We suggest that differences in water column structure and internal wave activity drive intermittent high production events in a predominantly oligotrophic sea.

The early larval developmental stages of the spiny lobster Panulirus ornatus (Fabricius, 1798) cultured under laboratory conditions

[Phyllosomas of the ornate spiny rock lobster Panulirus ornatus (Fabricius, 1798) were hatched and reared under laboratory conditions. The phyllosomas moulted 9 times to reach the sixth developmental stage, with distinct morphological changes between each stage, though not always between each moult. P. ornatus were much smaller and less developed than temperate species, but the early developmental stages of this species were very similar to those of P. homarus (Linnaeus, 1758). Early phyllosomas of P. ornatus were compared to those of closely related species. Im Labor geschlupfte Phyllosomalarven der tropischen Langustenart Panulirus ornatus (Fabricius, 1798) wurden unter kontrollierten Bedingungen aufgezogen. Die Larven hauteten sich neunmal und erreichten so das sechste Entwicklungsstadium. Dabei zeigten sich deutliche morphologische Veranderungen zwischen den einzelnen Stadien, nicht jedoch zwischen jedem Hautungszyklus. Larven von P. ornatus waren wesentlich kleiner und weniger entwickelt als temperaten Arten, aber fruhe Entwicklungsstadien waren denen von P. homarus (Linnaeus, 1758) sehr ahnlich. Die fruhen Phyllosomas von P. ornatus werden mit denen nah verwandter Arten verglichen., Phyllosomas of the ornate spiny rock lobster Panulirus ornatus (Fabricius, 1798) were hatched and reared under laboratory conditions. The phyllosomas moulted 9 times to reach the sixth developmental stage, with distinct morphological changes between each stage, though not always between each moult. P. ornatus were much smaller and less developed than temperate species, but the early developmental stages of this species were very similar to those of P. homarus (Linnaeus, 1758). Early phyllosomas of P. ornatus were compared to those of closely related species. Im Labor geschlupfte Phyllosomalarven der tropischen Langustenart Panulirus ornatus (Fabricius, 1798) wurden unter kontrollierten Bedingungen aufgezogen. Die Larven hauteten sich neunmal und erreichten so das sechste Entwicklungsstadium. Dabei zeigten sich deutliche morphologische Veranderungen zwischen den einzelnen Stadien, nicht jedoch zwischen jedem Hautungszyklus. Larven von P. ornatus waren wesentlich kleiner und weniger entwickelt als temperaten Arten, aber fruhe Entwicklungsstadien waren denen von P. homarus (Linnaeus, 1758) sehr ahnlich. Die fruhen Phyllosomas von P. ornatus werden mit denen nah verwandter Arten verglichen.]

Zooplankton Growth, Respiration and Grazing on the Australian Margins of the Tropical Indian and Pacific Oceans.

The specific activity of aminoacyl-tRNA synthetases (spAARS), an index of growth rate, and of the electron transport system (spETS), an index of respiration, was measured in three size fractions (73–150 μm, >150 μm and >350 μm) of zooplankton during five cruises to tropical coastal waters of the Kimberley coast (North West Australia) and four cruises to waters of the Great Barrier Reef (GBR; North East Australia). The N-specific biomass of plankton was 3–4-fold higher in the Kimberley than on the GBR in all 3 size classes: Kimberley 1.27, 3.63, 1.94 mg m-3; GBR 0.36, 0.88 and 0.58 mg m-3 in the 73–150 μm, >150 μm and >350 μm size classes, respectively. Similarly, spAARS activity in the Kimberley was greater than that of the GBR: 88.4, 132.2, and 147.6 nmol PPi hr-1 mg protein -1 in the Kimberley compared with 71.7, 82.0 and 83.8 nmol PPi hr-1 mg protein -1 in the GBR, for the 73–150 μm, >150 μm and >350 μm size classes, respectively. Specific ETS activity showed similar differences in scale between the two coasts: 184.6, 148.8 and 92.2 μL O2 hr-1 mg protein-1 in the Kimberley, against 86.5, 88.3 and 71.3 μL O2 hr-1 mg protein-1 in the GBR. On the basis of these measurements, we calculated that >150 μm zooplankton grazing accounted for 7% of primary production in the Kimberley and 8% in GBR waters. Area-specific respiration by >73 μm zooplankton was 7-fold higher in the Kimberley than on the GBR and production by >150 μm zooplankton was of the order of 278 mg C m-2 d-1 in the Kimberley and 42 mg C m-2 d-1 on the GBR. We hypothesize that the much stronger physical forcing on the North West shelf is the principal driver of higher rates in the west than in the east of the continent.

Plankton Respiration, Production, and Trophic State in Tropical Coastal and Shelf Waters Adjacent to Northern Australia

In a changing ocean, tropical waters can be instructive as to the potential effects of climate induced changes on marine ecosystem structure and function. We describe the relationships between planktonic community respiration (CR), net community production (NCP), gross primary production (GPP) and environmental variables in 14 regions and three ecosystem types (coastal, coral reef and open sea) from Australia, Papua New Guinea and Indonesia. The data are compiled from separate studies conducted between 2002 and 2014 with the goal of better parameterizing the metabolic balance in tropical marine waters. Overall, these regions were strongly autotrophic (average GPP:CR ratio: 2.14 ± 0.98), though our dataset of 783 paired measurements did include some oceanic stations where heterotrophy (GPP:CR < 1) was predominant, and some coastal stations that were intermittently heterotrophic. Our statistical analysis suggested that temperature was the most important determinant of CR in coral reef and ocean ecosystems but less so in coastal ecosystems, where chlorophyll concentration was more important. In contrast, chlorophyll and sampling depth were more important in regulating GPP than temperature. The relationships between temperatures and metabolic rates showed that these were ecosystem-dependent, with coastal ecosystems showing less response to temperature than coral reef and open sea sites. The threshold of GPP to achieve metabolic balance fell in a range between 0.715 mmol O2 m-3 d-1 in the Coral Sea to 10.052 mmol O2 m-3 d-1 in mangrove waterways of Hinchinbrook Channel. These data allow regions in and around northern Australia to be ranked in terms of trophic state, ranging from the oligotrophic Scott Reef (GPP:CR = 0.84 ± 0.08) to productive surface waters of the Kimberley coast (GPP:CR = 5.21 ± 0.62). The measurement of pelagic metabolism shows potential as a quantitative tool to monitor the trophic state of coastal waters.