Inshore Sites Research Articles

Recovery from bleaching is mediated by threshold densities of background thermo-tolerant symbiont types in a reef-building coral

Sensitive molecular analyses show that most corals host a complement of Symbiodinium genotypes that includes thermo-tolerant types in low abundance. While tolerant symbiont types are hypothesized to facilitate tolerance to temperature and recovery from bleaching, empirical data on their distribution and relative abundance in corals under ambient and stress conditions are still rare. We quantified visual bleaching and mortality of coral hosts, along with relative abundance of C- and D-type Symbiodinium cells in 82 Acropora millepora colonies from three locations on the Great Barrier Reef transplanted to a central inshore site over a 13 month period. Our analyses reveal dynamic change in symbiont associations within colonies and among populations over time. Coral bleaching and declines in C- but not D-type symbionts were observed in transplanted corals. Survival and recovery of 25% of corals from one population was associated with either initial D-dominance or an increase in D-type symbionts that could be predicted by a minimum pre-stress D : C ratio of 0.003. One-third of corals from this population became D dominated at the bleached stage despite no initial detection of this symbiont type, but failed to recover and died in mid to late summer. These results provide a predictive threshold minimum density of background D-type symbionts in A. millepora, above which survival following extreme thermal stress is increased.

Variation in the composition of corals, fishes, sponges, echinoderms, ascidians, molluscs, foraminifera and macroalgae across a pronounced in-to-offshore environmental gradient in the Jakarta Bay–Thousand Islands coral reef complex

Substrate cover, water quality parameters and assemblages of corals, fishes, sponges, echinoderms, ascidians, molluscs, benthic foraminifera and macroalgae were sampled across a pronounced environmental gradient in the Jakarta Bay–Thousand Islands reef complex. Inshore sites mainly consisted of sand, rubble and turf algae with elevated temperature, dissolved oxygen, pH and chlorophyll concentrations and depauperate assemblages of all taxa. Live coral cover was very low inshore and mainly consisted of sparse massive coral heads and a few encrusting species. Faunal assemblages were more speciose and compositionally distinct mid- and offshore compared to inshore. There were, however, small-scale differences among taxa. Certain midshore sites, for example, housed assemblages resembling those typical of the inshore environment but this differed depending on the taxon. Substrate, water quality and spatial variables together explained from 31% (molluscs) to 72% (foraminifera) of the variation in composition. In general, satellite-derived parameters outperformed locally measured parameters.

Decoupled Seasonal Stress as an Indication of Chronic Stress in <i>Montastraea cavernosa</i> and <i>Porites astreoides</i> Inhabiting the Florida Reef Tract

Although mass mortality from disease and climate anomalies are largely to blame for rapid losses in coral cover along the Florida reef tract, the failure of extant populations to recolonize the offshore zone is puzzling given improvements to water quality and narrower range in seawater temperature compared to the inshore patch reef zone. Using existing data from the Coral Reef Environmental Monitoring Program (CREMP) and from an inshore and offshore site established to compliment this dataset we identified significantly increased abundance and diversity of scleractinian coral from inshore to offshore across the Florida reef tract. Applying exploratory statistical methods we identified two abundant species, Montastraea cavernosa and Porites astreoides , inhabiting both zones to varying degrees. Following reciprocal transplantation of conspecifics between a representative offshore and inshore reef (6 m depth), we monitored monthly coral colony brightness (a measurement related to endosymbiotic dinoflagellate density) over a two-year period to examine symbiont loss, a common stress response in scleractinian corals. Although species-specific stress patterns were not identified, zone-specific variation was evident. Trigonometric regression of stress level by month revealed a significant relationship supporting an annual stress and recovery period at the inshore patch reef zone. Contrary to this result, conspecifics transplanted to the offshore zone did not display recovery resulting in a continued chronically bleached state over the two-year period. Our results implicate alleviation or decreased stress at inshore sites and the importance of extending greater protection to reefs within this zone.

DINÁMICA OCÉANO-ATMÓSFERA Y SU INFLUENCIA EN LA BIOMASA FITOPLANCTÓNICA, EN LA ZONA COSTERA DEL DEPARTAMENTO DEL MAGDALENA, CARIBE COLOMBIANO

From February to June 2008 at inshore sites of the Magdalena region, specifically in Gaira and Granate inlets and Taganga Bay, six field trips were done comparing the main dry and short rainy seasons. The main aim was to determine the coupled ocean-atmosphere influence on the upwelling intensity, considering the physical and chemical variability within the water column between 0 and 60 m and the response of the phytoplankton community measured as chlorophyll a. Atmospheric, oceanographic, and biological conditions were evaluated following the Eulerian method. According to the oceanic and atmospheric conditions during the research period, Ekman transport and continental upwelling processes occurred through February and April, in response to adequate conditions: average wind speed (>4.0 m/s) and wind direction (parallel and perpendicular to the coast). Physical and chemical anomalies were detected in the water mass, such as low temperature (25.34±0.82°C), high salinity (35.5±0.30) and oxygen subsaturation (70.6±7.8 %). The inorganic nutrient supply was higher during upwelling processes,consequently, the system was defined as mesotrophic, causing greater phytoplankton chlorophyll a biomass with level up to 1.60 μg/L. "La Niña" 2007/2008 event, which covered the period of this of this research, did not incite any important disturbance over the typical upwelling conditions.

Coral growth patterns of Montastraea cavernosa and Porites astreoides in the Florida Keys: The importance of thermal stress and inimical waters

The calcification and extension rates of two species of scleractinian coral (Montastraea cavernosa, Porites astreoides) were measured in corals experimentally transplanted to paired inshore and offshore locations in the Upper, Middle, and Lower Florida Keys from 2010 to 2011. Growth rates were compared with respect to 1) shelf location, 2) species, 3) region, and 4) temperature. Transplanted corals on inshore reefs generally calcified less than those at paired offshore sites, but these differences were only significant in a few cases. This difference in growth is likely because of two thermal stress events that occurred inshore, but not offshore, as growth records from cores of P. astreoides revealed significantly higher extension and calcification inshore from 2001–2013. The core data confirmed that the years 2010–2012 were a period of depressed growth inshore. Calcification and extension rates of the experimental corals were not statistically different between M. cavernosa and P. astreoides within a given site. The only exceptions were that calcification was higher in M. cavernosa at the Middle Keys inshore site. The Middle Florida Keys sites had the lowest rates of calcification, supporting the hypothesis that the influence of Florida Bay waters in this region contributes to poor reef development. Mean calcification rates negatively correlated with metrics of cold stress in M. cavernosa and heat stress in P. astreoides. The lack of a significant correlation between heat stress and mean calcification in M. cavernosa may help explain this species persistence on today's reefs. Maximum calcification and mean extension, however, were negatively correlated with maximum running 30-day mean temperature, showing that the growth of M. cavernosa is not completely insensitive to warm water stress. The ‘weedy’ life-history strategy of P. astreoides may compensate for the sensitivity of calcification rates to heat stress reported here, allowing this species to maintain the stable populations that have been observed throughout Florida and the wider Caribbean.

How does Calanus helgolandicus maintain its population in a variable environment? Analysis of a 25-year time series from the English Channel

Calanus helgolandicus is a key copepod of the NE Atlantic and fringing shelves, with a distribution that is expanding northwards with oceanic warming. The Plymouth L4 site has warmed over the past 25-years, and experiences large variations in the timing and availability of food for C. helgolandicus. Here we examine the degree to which these changes translate into variation in reproductive output and subsequently C. helgolandicus population size. Egg production rates (eggs female−1 day−1) were maximal in the spring to early-summer period of diatom blooms and high ciliate abundance, rather than during the equally large autumn blooms of autotrophic dinoflagellates. Egg hatch success was lower in spring however, with a greater proportion of naupliar deformities then also. Both the timing and the mean summer abundance of C. helgolandicus (CI–CVI) reflected those of spring total reproductive output. However this relationship was driven by inter-annual variability in female abundance and not that of egg production per female, which ranged only two-fold. Winter abundance of C. helgolandicus at L4 was much more variable than abundance in other seasons, and reflected conditions from the previous growing season. However, these low winter abundances had no clear carry-over signal to the following season’s population size. Overall, the C. helgolandicus population appears to be surprisingly resilient at this dynamic, inshore site, showing no long-term phenology shift and only a four-fold variation in mean abundance between years. This dampening effect may reflect a series of mortality sources, associated with the timing of stratification in the early part of the season, likely affecting egg sinking and loss, plus intense, density-dependent mortality of early stages in mid-summer likely through predation.

New puerulus collector design suitable for fishery-dependent settlement monitoring

Abstract Fishery-independent diver-based puerulus settlement monitoring has been conducted for over two decades in sheltered inshore shallow sites on the Tasmanian coast and has been utilized in the development of a predictive capacity for the Tasmanian lobster fishery. However, the majority of catches in this fishery are sourced from deep (>50 m), remote, and highly exposed areas where it is impractical and expensive to conduct fishery-independent routine settlement monitoring. To determine if pueruli settle in deeper waters, we adapted a crevice puerulus collector to fit within a lobster trap frame specifically designed to be deployed and serviced by vessels typical of the Tasmanian lobster fleet. A 5-month trial yielded puerulus catches similar to those from inshore shallow sites including recording puerulus from waters more than 100 m depth. The collector design was reported by fishers to be safe and convenient to service in regions exposed to strong westerly winds and swell more than 7 m. This collector will allow a cost-effective fishery-dependent approach to puerulus settlement monitoring utilizing commercial fishers for field operations and researchers for administration, sorting, and analysis.

Residency and movement dynamics of southern rock lobster (Jasus edwardsii) after a translocation event

Previous movement studies on the southern rock lobster (Jasus edwardsii) have all involved releasing tagged animals at the point of capture. In 2007, 5298 lobsters, in total, were tagged and translocated from an offshore site (>100-m depth) to two inshore sites (<20-m depth) in South Australia. After a period of 735 days, 510 (9.6%) had been recaptured. The majority of translocated lobsters were located within close proximity to the release points, with 306 (60%) having moved <5km. Of the remainder, 133 (26%) were recaptured within 5–10km, with a further 71 (14%) individuals having moved >10km. Movement patterns were highly directional in nature, with individuals consistently travelling in a south-west bearing, regardless of distance moved. In almost all cases, movement was from inshore to offshore sites, with female lobsters travelling significantly further (mean 5.66km ±6.41s.d.) than males (mean 5.02km ±9.66s.d.). The results are consistent with previous large-scale tagging studies of J. edwardsii, which indicated high residency levels but with occasional directed movement by some individuals.

Feeding rates and prey selectivity of planktonic decapod larvae in the Western English Channel

Meroplankton are seasonally important contributors to the zooplankton, particularly at inshore sites, yet their feeding ecology is poorly known relative to holoplankton. While several studies have measured feeding in decapod larvae, few studies have examined the feeding rates of decapod larvae on natural prey assemblages throughout the reproductive season. We conducted 8 feeding experiments with Necora puber, Liocarcinus spp. and Upogebia spp. zoea larvae collected from the L4 monitoring site off Plymouth (50°15.00′N, 4°13.02′W) during spring–summer 2009 and 2010. This period spanned moderate-to-high food availability (0.5–1.6 µg chl-a L−1), but a great range in food composition with small cells <20 µm dominating in 2010. Daily rations averaged 17, 60 and 22 % of body C for the 3 respective decapod species. Clearance rates differed according to prey type, and all 3 decapod genera showed evidence of selection of dinoflagellates. Importantly, small cells including nano- and pico-plankton were ingested, this being demonstrated independently by flow cytometric analysis of the feeding experiments and molecular analysis. PCR-based analysis of the haptophyte portion of the diet revealed ingestion of Isochrysis galbana by decapod larvae in the bottle incubations and Isochrysis galbana and Phaeocystis globosa by decapod larvae collected directly from the field. This study has shown that pico- and nano-sized plankton form an important supplement to the diverse and variable diet of decapod larvae.

The interaction of environment and genetic diversity within meadows of the seagrass Posidonia australis (Posidoniaceae)

Understanding the extent and impact of factors influencing the levels and structur- ing of genetic diversity within natural populations is a key objective of ecological genetics. For marine angiosperms, variation in abiotic environmental factors at the local scale can have a major influence on levels of clonality and spatial genetic structure, and thus influence mating systems, sexual reproduction, and recruitment. Identifying the key drivers of genetic structuring is critical for genetic management of ecological restoration success, especially in systems where the nature and extent of clonality is highly variable. Here, we quantify clonality and patterns of genetic structure in the temperate Australian seagrass Posidonia australis. We examine the loca- tion of meadows in relation to water movement and prevailing winds to assess their relative influence on local spatial genetic structuring. Measures of genetic diversity, assessed with 7 polymorphic microsatellite loci, were highly variable across 13 meadows sampled within and around a natural embayment on the west coast of Australia. The overall structure of P. australis meadows across this region is best explained as one of 'chaotic' genetic patchiness, with signifi- cant differentiation among most meadows (pairwise FST values), high levels of genetic diversity in meadows that are in more open waters, and lower genetic diversity at inshore sites facing strong prevailing winds at the time of seed dispersal or that have little water movement. A strong isolation by distance relationship within the embayment is consistent with prevailing winds (which create surface currents) at the time of peak pollen and seed release, strongly influencing dispersal direction.

Stable isotope ratios reveal food source of benthic fish and crustaceans along a gradient of trophic status in the East China Sea

The East China Sea (ECS) receives large quantities of particulate organic matter (POM) and inorganic nutrients transported from the Changjiang (Yangtze River), which have produced high productivity in the northwestern ECS. This study evaluated potential contributions of terrigenous POM (allochthonous food source) and nutrient-induced marine production (autochthonous source) to the ECS benthic ecosystem by analyzing stable isotopic compositions of phytoplankton, zooplankton, benthic crustaceans and fish. Benthic consumers exhibited δ13C values similar to those of their autochthonous food sources (i.e., phytoplankton and zooplankton), revealing their major reliance on marine production. In contrast, the δ13C values of benthic fish (−19.6‰ to −13.5‰) and crustaceans (−18.9‰ to −15.0‰) were much higher than that of terrigenous POM (−25.7‰), which generally accounted for less than 20% of the most fish diet. Phytoplankton and zooplankton generally exhibited higher δ13C values at eutrophic and highly productive inshore sites than at oligotrophic offshore sites. This enrichment of inshore δ13C values was mainly attributed to lower photosynthetic fractionation during algal blooms, an effect that was further enhanced during flood period of the Changjiang. The δ13C values of demersal fish assemblages were also significantly higher at inshore sites and decreased seaward. However, fish δ15N values and their estimated trophic levels showed relatively small spatial variation. The disproportionate variations in δ13C and δ15N values suggested that the enriched C isotopic signatures derived from an elevated δ13C baseline of the inshore food web instead of trophic enrichment of the isotopic ratios. The significantly positive correlations between concentrations of chlorophyll a and nutrients versus fish δ13C provided further evidence for the use of pelagic algal bloom materials by inshore consumers. The isotopic and oceanographic survey data suggested that inorganic nutrients discharged from the Changjiang River nourish benthic consumers in the ECS and play an important role in linking marine benthic ecosystems to local pelagic primary production as well as to the adjacent terrestrial watershed.

Influence of Age‐1 Conspecifics, Sediment Type, Dissolved Oxygen, and the Deepwater Horizon Oil Spill on Recruitment of Age‐0 Red Snapper in the Northeast Gulf of Mexico during 2010 and 2011

AbstractThe Deepwater Horizon oil spill was one of the largest oil spills in U.S. history. The timing of this spill coincided with peaks in spawning and recruitment of Red Snapper Lutjanus campechanus and may have led to reduced recruitment or to year‐class failure. Artificial recruitment reefs were deployed in 2010 (n = 30) and 2011 (n = 30) to measure Red Snapper recruitment off the coast of Alabama at four sites (three inshore sites, 13 km south: west, center, and east sites, each 30 km apart; and one offshore site, 25 km south). Substantial age‐0 Red Snapper recruitment (density range = 0–34.5 fish/m3) occurred in 2010, with higher densities on inshore reefs than on offshore reefs. Age‐0 Red Snapper recruitment was again observed in 2011 (density range = 0–108.5 fish/m3) along with age‐1 Red Snapper (density range = 0–78.9 fish/m3) from the 2010 year‐class. There was a negative correlation between the densities of age‐0 and age‐1 Red Snapper, indicating that older Red Snapper excluded younger fish from the reefs. Higher fractions of silt in the substrate at the west site compared with the center and east sites were associated with higher densities of age‐0 Red Snapper, but the effects of sediment type were less important than exposure to hypoxic conditions at the west site in late August 2011 (dissolved oxygen fell to concentrations as low as 0.4 mg/L), which caused an almost complete loss of fish. The abundances of age‐0 and age‐1 Red Snapper in 2010 and 2011 provide evidence that the oil spill did not result in a year‐class failure and that the most important variables affecting age‐0 Red Snapper abundances were age‐1 Red Snapper presence and dissolved oxygen concentration.Received August 23, 2013; accepted December 19, 2013

Summer circulation dynamics within the Perth coastal waters of southwestern Australia

The dynamics of the summer circulation in the coastal waters off Perth in Western Australia were investigated during a two-month field experiment. The study included the deployment of an array of moorings spanning the outer shelf, the inner shelf, within the inshore Perth coastal lagoon, and in the large coastal embayment of Cockburn Sound. The results revealed highly transient coastal circulation patterns that responded to variability in both the locally- and remotely-generated forcing. Local wind forcing played a primary role in driving much of the alongshore current variability at the shallower (<20m depth) inshore sites, with a well-defined peak wind forcing time scale of ~1 week that fell within the synoptic weather band in the region. Due to the mean northward wind stress that persisted during this summer period, a mean northward current of 0.05–0.1ms−1 was observed at these inshore sites. Large-scale variations in alongshore water level (pressure) gradients also episodically generated strong along- and cross-shore current oscillations throughout the region. Major events were associated with the propagation of coastally-trapped waves generated by a tropical low pressure system far (~1000km) to the north of Perth, which propagated down the Western Australia coast. On the outer shelf, local wind forcing played a minor (but still not a negligible) role in driving alongshore current variability, with this momentum balance instead dominated by the alongshore pressure gradient variability. Due to the unusually large alongshore pressure gradient that persists year round along the Western Australia coast, currents on the shelf were on average southward. However, large-scale northward reversals of the shelf flow were also observed when northward wind stresses were sufficiently large and/or the local alongshore pressure gradient became episodically weak.

Evidence for thermally mediated settlement in lobster larvae (Homarus americanus)

We examined the potential for bottom temperatures ≤12 °C to inhibit successful recruitment of planktonic lobster postlarvae to the benthos. In laboratory trials, postlarvae held at 11 °C exhibited higher mortality, slower development, and reduced size increase at molt relative to postlarvae held at 13 °C. We sampled at field sites within Machias Bay, Maine (mean bottom temperature 12.39 °C, 46.1 degree-days ≥12 °C) and at the mouth of the bay (mean bottom temperature 11.57 °C, 5.1 degree-days ≥12 °C), where temperature was influenced by the cold Eastern Maine Coastal Current (EMCC). We found significantly higher settlement at the warm inshore site but, the abundance of competent planktonic postlarvae was not significantly different between sites, indicating a disconnect between postlarval abundance and settlement. Regional sampling of newly settled lobsters revealed a pattern of higher settlement at inshore sites extending across a broader coastal region impacted by the EMCC. Our results suggest that small differences in water temperature may shape settlement patterns through either behavioral avoidance of colder settlement sites or elevated postsettlement mortality of postlarvae settling at colder sites.

Effects of stocking density on survival, growth and biochemical composition of cultured mussels (Mytilus galloprovincialis, Lamarck 1819) from an offshore submerged longline system

AbstractThis study examined an offshore submerged mus-sel longline system, in the Black Sea, from May2009 to May 2010. The system was allowed1 year for spat collection. After a 1-year spat col-lection period, some spat collectors were leftuntouched (NS), and some spat collectors weregrazed and socked (S) for a grow-out study in May2009. The effects of stocking density on thegrowth and survival of the S and NS mussels wereexamined. The biochemical composition of the mus-sels was also determined. Environmental factorsincluding temperature, salinity, chlorophyll a, totalsuspended matter, inorganic matter and organicmatter were monitored monthly during the experi-mental period. In May 2010, the mean length andlive weight of the S and NS mussels were60.46 0.60 mm and 53.34 0.37 mm, respec-tively, and 20.50 0.50 g and 13.11 0.26 grespectively. Mean moisture and ash were 82.35 0.47% and 6.67 0.44% respectively. Mean car-bohydrate, protein and lipid were 27.74 2.40%,57.68 2.15% and 7.91 0.68% respectively.These results indicate that a submerged offshoremussel culture system in the Black Sea can becommercially convenient. In addition, stock man-agement via thinning out of the spat can consider-ably increase the marketable size of mussels,reduce harvest time and produce better growth.Keywords: Mussel, offshore, density, growth,survival, biochemicalIntroductionUnited Nations Food and Agricultural Organiza-tion (FAO) statistics indicates that mussels are oneof the most popular cultured species. The culturingof mussels has increased from 1307 thousandtonnes to 1812 thousand tonnes in the last fewdecades (FAO/Fishstat Plus 2012).For a long time, mussel farms have been limitedto sheltered coastal lagoons (Burbridge, Hendrick,Roth & Rosenthal 2001). According to Danioux,Loste and Paquotte (1997), coastal lagoons haverich and easily accessible but fragile environmentsthat have been exploited to their maximum spatialand biological capacity. These researchers havealso stated that several risk factors, at times simul-taneously, have limited the expansion of themussel farming activity in the restricted lagoonenvironment: (i) the necessary intensification ofproduction to reduce production costs; (ii) pollu-tion from industrial and domestic sources, whichproduces high mortality at times and (iii) thelimited renewal of the environment due to a lackof strong tides, which brings with it a dystrophiccrisis and anoxia risk. Inshore sites have alsoproven to have lower growth and higher diseaserates, with greater risks of contamination fromoveruse and other activities. Due to these chal-lenges, to date, the mussel production achievedhas not increased enough to meet demand. As aresult, offshore mussel culture has been suggestedas a solution to meet the growing demand(Langan 2008).

Characterization of a toxic Pseudo-nitzschia spp. bloom in the Northern Gulf of Mexico associated with domoic acid accumulation in fish

A toxic bloom of Pseudo-nitzschia spp. was observed in the Alabama coastal waters of the northern Gulf of Mexico (NGOM) in June 2009 that resulted in the accumulation of domoic acid (DA) in fish. The bloom initiated following a large storm event that likely caused increased groundwater discharge 16–20 days prior to peak densities. Eleven sites, located in littoral shoreline waters and inshore embayments spanning the entire Alabama NGOM coastline, were sampled during peak densities to assess Pseudo-nitzschia species composition and toxicity, and associated water-quality parameters. Small fish (0.27–11.9g body weight) were collected at six of these sites for analysis of DA content. High Pseudo-nitzschia spp. densities (8.27×104–5.05×106celll−1) were detected at eight sites located in the littoral shoreline and particulate DA was detected at six of these littoral sites (48.0–540pgml−1). The bloom consisted primarily (>90%) of Pseudo-nitzschia subfraudulenta, a species previously characterized as forming only a minor component of Pseudo-nitzschia assemblages and not known to produce DA. Pseudo-nitzschia spp. were at low densities or not detected at the inshore sites and DA was detected at these sites. Pseudo-nitzschia spp. density varied along an estuarine gradient, with greater densities occurring in the most saline, clear, and nutrient-poor waters. Cell density was strongly and negatively correlated with silicate (Si) concentrations and the ratios of silicate to dissolved inorganic nitrogen and phosphate (Si:DIN and Si:PO4). Cell toxin quota was negatively correlated with phosphate, and strongly and positively correlated with the ratio of total nitrogen to total phosphorus (TN:TP). These relationships are consistent with previous observations that indicate Pseudo-nitzschia spp. density and toxicity are likely to be greater in high salinity, high irradiance, and nutrient-poor waters. DA was detected in 128 of 131 (98%) of the fish collected, which included seven primary and secondary consumer species. This is the first demonstration of trophic transfer of DA in this region of the NGOM, indicating that toxic blooms of Pseudo-nitzschia spp. in Alabama coastal waters have the potential to transfer DA to recreationally and commercially important fish species.

Spatial patterns of bacterial community composition within Lake Erie sediments

Lake Erie is a large freshwater ecosystem with three distinct basins that exhibit an east-to-west gradient of increasing productivity, as well as allochthonous inputs of nutrients and xenobiotics. To evaluate microbial community composition throughout this ecosystem, 435 16S rDNA environmental clones were sequenced from 11 sediment samples throughout the Western, Central, and Eastern basins, as well as the hypoxic “dead zone” of Lake Erie in the hypolimnetic region of the Central basin. Rank abundance distributions of bacterial taxa within each location revealed that Gamma- and Betaproteobacteria, microbes capable of metabolizing a wide range of organic matter pools, comprised a greater fraction of the microbial community within inshore sites of the Central and Western basins compared to the Eastern basin. While geophysical characteristics of the three major basins and the dead zone did not drive significant differences in species diversity, Fast UniFrac analyses revealed microbial community spatial structuring, with the Central basin showing higher phylogenetic uniqueness of bacterial lineages. Principal component analyses based on phylogenetic distances consistently grouped the dead zone with the Central basin and highlighted the distinctiveness of microbial communities from the Eastern basin. Results from this study provide evidence for the local adaptation of microbial communities and the potential role of riverine inputs in modulating taxonomic composition of lacustrine bacterial communities. These results are consistent with previous functional studies on microbial metabolism, which showed that differences in geochemistry across the three basins of Lake Erie play an important role in the local adaptation of microbial communities.

Can simple phosphorus mass balance models guide management decisions? A case study in the Bay of Quinte, Ontario, Canada

We test the capacity of an existing simple mass-balance total phosphorus (TP) model to evaluate nutrient loading scenarios in the Bay of Quinte, Ontario, Canada. Our study examines whether model parameters and loading inputs are well characterized and relevant to the current conditions in the Bay of Quinte and its drainage areas. We also identify critical data gaps and influential assumptions in regard to the uncertainty of model outputs and the credibility of predictive statements about the achievability of delisting objectives of the system. Our analysis shows that the model closely reproduced the observed variability of the TP seasonal averages during the calibration period 1972–2001, but its performance was significantly reduced when the actual predictive capacity was assessed in the 2002–2009 validation period. The most troublesome result is the inability of the model to reproduce the observed TP variability at temporal scales that are more meaningful from an environmental management point of view (i.e., monthly averages or daily snapshots from the system). Sensitivity analysis shows that several parameters associated with the role of the sediments were significant drivers of the model outputs, suggesting that considerable uncertainty exists in regard to the characterization of the sediments. The loadings from Trent River and the TP levels of the inflowing water masses from Lake Ontario predominantly shape the variability in the upper and lower segments of the Bay of Quinte, respectively. We also present a critical review of the suitability of the existing water quality criteria to depict the trophic status throughout the system. Our study contends that the summer average TP concentrations do not adequately reflect the prevailing conditions and that the development of proper water quality criteria should place more emphasis on inshore sites, where the eutrophication problems are more frequently manifested. Finally, we pinpoint factors unaccounted for by the original model that are likely to modulate the response of the system in its present state. We also discuss important directions of model structure augmentation and ways to optimize the spatial segmentation.

Denitrification, anammox and nitrate reduction in sediments of the southern Great Barrier Reef lagoon

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 478:57-70 (2013) - DOI: https://doi.org/10.3354/meps10040 Denitrification, anammox and nitrate reduction in sediments of the southern Great Barrier Reef lagoon Dirk V. Erler*,1, Lindsay A. Trott2, Daniel M. Alongi2, Bradley D. Eyre1 1Centre for Coastal Biogeochemistry, School of Environmental Science and Management, Southern Cross University, Lismore NSW 2480, Australia. 2Australian Institute of Marine Science, PMB 3, Townsville MC QLD 4810, Australia *Email: dirk.erler@scu.edu.au ABSTRACT: We provide the first reported estimates of anammox activity in tropical continental shelf sediments (southern section of the Great Barrier Reef lagoon; GBRL). The measured contribution of anammox to total N2 production was up to 70% but restricted to only 1 of the 4 (2 inshore and 2 offshore) sites assayed. Sediment characteristics (contents of total organic carbon [TOC] and manganese [Mn], C:N ratio) at this site appeared to favour anammox activity and the estimated maximum rate was 4.9 µmol m-2 h-1. Anammox bacteria may be a significant contributor to N2 production along the coastal zone of the GBRL. The availability of labile (low C:N) TOC seemed to drive denitrification to completion in the offshore sediments. However, rates of NO3- reduction to NH4+ at the offshore sites were comparable to or higher than denitrification rates. It was unclear whether dissimilatory or assimilatory processes were responsible for the observed reduction of NO3- to NH4+ at the offshore sites. At the 2 inshore sites, NO3- reduction to NH4+ was a larger sink for NO3- than denitrification. Anammox does exist in the tropical continental shelf sediments of the GBRL and should be studied further to determine its role in larger scale N cycling. The roles of assimilatory and dissimilatory nitrate reduction to ammonium also need to be assessed within the GBRL. KEY WORDS: Great Barrier Reef · Anammox · Dissimilatory/assimilatory nitrate reduction to ammonia · Denitrification Full text in pdf format PreviousNextCite this article as: Erler DV, Trott LA, Alongi DM, Eyre BD (2013) Denitrification, anammox and nitrate reduction in sediments of the southern Great Barrier Reef lagoon. Mar Ecol Prog Ser 478:57-70. https://doi.org/10.3354/meps10040 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 478. Online publication date: March 25, 2013 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2013 Inter-Research.

Cross-shelf variation in the structure of molluscan assemblages on shallow, rocky reefs in subtropical, eastern Australia

Despite the fact that molluscs are one of the most widespread and conspicuous of all marine invertebrates, comparatively little is known about their ecology, especially with respect to biological interactions that drive community processes. We consequently assessed patterns of subtidal mollusc assemblages on subtropical rocky reefs in the Solitary Islands Marine Park (SIMP), eastern Australia. Shelled molluscs (specifically shelled gastropods and bivalves) were targeted to test if: (1) mollusc assemblages change with increasing distance from shore; (2) reef orientation (vertical and horizontal reef faces) influences assemblage structure; (3) sessile benthic communities influence the composition of mollusc assemblages. Multivariate analyses of community patterns indicated strong cross-shelf patterns. However, no significant differences were found for summary community variables (species richness, total abundance). Inshore sites were dominated by large herbivores (especially turbinids) and prey-specific ranellids. Mid-shelf assemblages comprised a mix of taxa that occurred in both inshore and offshore assemblages and were thus transitional between these shelf positions. Offshore assemblages were distinctly different to reefs closer to shore and were characterised primarily by the presence of sedentary (Vermetidae and Chamidae), and tropically-affiliated taxa. Relationships with reef orientations were found to be inconsistent and correlations with sessile benthos were relatively weak. The overall patterns are similar to those found for corals and fish in the region and most likely reflect the increasing influence of the East Australian Current offshore.