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1.
Sci Total Environ ; 773: 145146, 2021 Feb 02.
Artigo em Inglês | MEDLINE | ID: mdl-33582324

RESUMO

Local differences in trophic structure and composition of organic matter subsidies can influence the capacity of soft sediment communities to assimilate recycled organic matter from processes such as salmon farm enrichment. The present study combines biochemical analysis with biomass density information on soft sediment taxa collected within the depositional footprint of salmon farms and at reference sites in the Marlborough Sounds, New Zealand. Distinct biochemical signatures confirmed that the flux of organic matter from salmon farms was an important subsidy for soft sediment communities. Isotopic modelling demonstrated that the proportion of biomass supported by farm-derived organic matter did not change in a consistent pattern along the 300 m gradient from each farm site, whereas the average trophic level of communities decreased with increasing proximity to farms. High variability in both the total biomass and the distribution of biomass across trophic levels occurred among sites downstream of farms and among individual farms. Consequently, estimates of basal organic matter assimilation per unit area by communities differed by several orders of magnitude among sites. Total organic matter assimilation tended to decrease with increasing proximity to farms due to a shift towards a more detrital based community. Differences in basal organic matter assimilation among farms did not appear to be directly related to local flow regime, but instead was closely linked to differences in the soft sediment community composition likely influenced by an array of anthropogenic and environmental factors. The results presented here highlight the importance of considering local variability in basal organic matter source pools, and the potential for synergistic and cumulative effects to drive changes in food web trophodynamics when assessing the impacts of aquaculture on soft sediment communities.

2.
Sci Rep ; 10(1): 16276, 2020 10 01.
Artigo em Inglês | MEDLINE | ID: mdl-33004918

RESUMO

On Conch Reef, Florida Keys, USA we examined the effects of reef hydrography and topography on the patterns of stable isotope values (δ18O and δ13C) in the benthic green alga, Halimeda tuna. During the summer, benthic temperatures show high-frequency fluctuations (2 to 8 °C) associated with internal waves that advected cool, nutrient-rich water across the reef. The interaction between local water flow and reef morphology resulted in a highly heterogenous physical environment even within isobaths that likely influenced the growth regime of H. tuna. Variability in H. tuna isotopic values even among closely located individuals suggest biological responses to the observed environmental heterogeneity. Although isotopic composition of reef carbonate material can be used to reconstruct past temperatures (T(°C) = 14.2-3.6 (δ18OHalimeda - δ18Oseawater); r2 = 0.92), comparing the temperatures measured across the reef with that predicted by an isotopic thermometer suggests complex interactions between the environment and Halimeda carbonate formation at temporal and spatial scales not normally considered in mixed sediment samples. The divergence in estimated range between measured and predicted temperatures demonstrates the existence of species- and location-specific isotopic relationships with physical and environmental factors that should be considered in contemporary as well as ancient reef settings.

3.
Sci Total Environ ; 693: 133507, 2019 Nov 25.
Artigo em Inglês | MEDLINE | ID: mdl-31377366

RESUMO

Systems with strong horizontal and vertical gradients, such as fjords, are useful models for studying environmental forcing. Here we examine microbial (prokaryotic and eukaryotic) community changes associated with the surface low salinity layer (LSL) and underlying seawater in multiple fjords in Fiordland National Park (New Zealand). High rainfall (1200-8000 mm annually) and linked runoff from native forested catchments results in surface LSLs with high tannin concentrations within each fjord. These gradients are expected to drive changes in microbial communities. We used amplicon sequencing (16S and 18S) to assess the impact of these gradients on microbial communities and identified depth linked changes in diversity and community structure. With increasing depth, we observed significant increases in Proteobacteria (15%) and SAR (37%), decreases in Opisthokonta (35%), and transiently increased Bacteroidetes (3% increase from 0 to 40 m, decreasing by 8% at 200 m). Community structure differences were observed along a transect from the head to the mouth, specifically 25% mean relative abundance decreases in Opisthokonta and Bacteroidetes, and increases in SAR (25%) and Proteobacteria (>5%) at the surface, indicating changes based on distance from the ocean. This provides the first in-depth view into the ecological drivers of microbial communities within New Zealand fjords.


Assuntos
Microbiota/fisiologia , Fitoplâncton/fisiologia , Água do Mar/química , Archaea/fisiologia , Fenômenos Fisiológicos Bacterianos , Estuários , Eucariotos , Nova Zelândia , Salinidade
4.
Glob Chang Biol ; 24(8): 3642-3653, 2018 08.
Artigo em Inglês | MEDLINE | ID: mdl-29704449

RESUMO

Organic matter produced by the sea ice microbial community (SIMCo) is an important link between sea ice dynamics and secondary production in near-shore food webs of Antarctica. Sea ice conditions in McMurdo Sound were quantified from time series of MODIS satellite images for Sept. 1 through Feb. 28 of 2007-2015. A predictable sea ice persistence gradient along the length of the Sound and evidence for a distinct change in sea ice dynamics in 2011 were observed. We used stable isotope analysis (δ13 C and δ15 N) of SIMCo, suspended particulate organic matter (SPOM) and shallow water (10-20 m) macroinvertebrates to reveal patterns in trophic structure of, and incorporation of organic matter from SIMCo into, benthic communities at eight sites distributed along the sea ice persistence gradient. Mass-balance analysis revealed distinct trophic architecture among communities and large fluxes of SIMCo into the near-shore food web, with the estimates ranging from 2 to 84% of organic matter derived from SIMCo for individual species. Analysis of patterns in density, and biomass of macroinvertebrate communities among sites allowed us to model net incorporation of organic matter from SIMCo, in terms of biomass per unit area (g/m2 ), into benthic communities. Here, organic matter derived from SIMCo supported 39 to 71 per cent of total biomass. Furthermore, for six species, we observed declines in contribution of SIMCo between years with persistent sea ice (2008-2009) and years with extensive sea ice breakout (2012-2015). Our data demonstrate the vital role of SIMCo in ecosystem function in Antarctica and strong linkages between sea ice dynamics and near-shore secondary productivity. These results have important implications for our understanding of how benthic communities will respond to changes in sea ice dynamics associated with climate change and highlight the important role of shallow water macroinvertebrate communities as sentinels of change for the Antarctic marine ecosystem.


Assuntos
Mudança Climática , Cadeia Alimentar , Camada de Gelo , Animais , Regiões Antárticas , Biomassa , Monitoramento Ambiental , Gelo , Microbiologia da Água
5.
J Phycol ; 47(3): 505-516, 2011 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-27021979

RESUMO

Spatial and temporal patterns of growth, erosion, productivity, and morphology of the dominant habitat-forming kelp Ecklonia radiata (C. Agardh) J. Agardh were studied bimonthly over 1.5 years in a southern New Zealand fjord characterized by strong gradients in light and wave exposure. Spatial differences in growth were observed with rates at two outer coast, high-light, wave-exposed sites reaching 0.42 and 0.45 cm · d-1 , respectively, compared to 0.27 cm · d-1 at an inner, more homogeneous site. Sporophyte productivity was similar among sites, although population productivity was greater at the outer sites due to population density being 5-fold greater than at the inner site. It was expected that the inner site would have no pronounced seasonal pattern in growth and productivity due to its homogeneity; however, all three sites displayed maximum rates in late winter/spring and minimal in autumn. Growth rates were 2-fold greater during the first growth period than the following year. This discrepancy was not correlated to inorganic nitrogen (N) levels, which remained low year-round (<4 µM), and is likely a result of an interaction between light and temperature, and the photosynthetic capability of E. radiata. Variable pigment content indicated photoacclimation at the inner site. Morphological differences were observed between sites, with E. radiata from the inner site having longer, wider, thinner blades and longer stipes. While E. radiata displayed spatial differences in growth, erosion, productivity, and morphology, populations displayed no temporal differences. These results highlight the need for greater understanding of the mechanisms influencing kelp growth and productivity in a unique marine environment.

6.
Ecology ; 88(4): 809-16, 2007 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-17536697

RESUMO

Forest litter is often considered to be a minor energy source to marine communities due to its refractory nature. Large volumes of forest litter are deposited in the New Zealand fjords, and likely recycled into available energy by microbial activity. In this study we used evidence from stable isotope analyses to test whether recycled carbon from chemoautotrophs was an important contributor to the diet of hagfish (Eptatretus cirrhatus). We then analyzed fatty acid biomarkers from the chemoautotrophic clam Solemya parkinsoni and E. cirrhatus to further discriminate the contribution of marine, terrestrial, and chemoautotrophic sources. Bulk isotopic signatures of E. cirrhatus varied considerably (delta13C, from -29.2 per thousand to -16.7 per thousand; delta15N, from -2.8 per thousand to +15.5 per thousand; delta34S, from -21.7 per thousand to +16.7 per thousand) and indicated that a significant percentage of organic matter (38-51%) originated from chemoautotrophs (delta13C, -31.3 per thousand +/- 0.1 per thousand [mean +/- SE]; delta15N, -5.7 per thousand +/- 0.2 per thousand; delta34S, -32.per thousand +/- 3.8 per thousand). Fatty acid biomarkers were depleted in 13C, particularly cis-vaccenic acid (18:1omega7: delta13C, -39.0 per thousand) indicating specific microbial origins of carbon. A high proportion of forest litter in sediments, coupled with isotopic and fatty acid biomarker results, indicates that terrestrial organic matter is a dominant contributor to this marine benthic system. This study demonstrates a clear linkage between terrestrial and marine ecological processes.


Assuntos
Fenômenos Fisiológicos da Nutrição Animal , Crescimento Quimioautotrófico/fisiologia , Ecossistema , Cadeia Alimentar , Feiticeiras (Peixe)/crescimento & desenvolvimento , Ração Animal , Animais , Isótopos de Carbono , Nova Zelândia , Isótopos de Nitrogênio , Solo/análise , Fatores de Tempo
7.
Mol Ecol ; 13(8): 2183-95, 2004 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-15245393

RESUMO

New Zealand's 14 deep-water fiords possess persistent salinity stratification and mean estuarine circulation that may serve to isolate populations of marine organisms that have a dispersal larval phase. In order to investigate this idea, we analysed the population structure of the sea star Coscinasterias muricata using a mitochondrial DNA marker. Genetic differentiation among populations of C. muricata was analysed using 366 base pairs of mtDNA D-loop. We compared populations from the fiords with several others sampled from around New Zealand. At a macro-geographical scale (> 1000 km), restricted gene flow between the North and South Islands was observed. At a meso-geographical scale (10-200 km), significant population structure was found among fiords and between fiords and open coast. The pattern of population genetic structure among the fiords suggests a secondary contact between a northern population and a southern one, separated by a contact or mixing zone. These populations may have diverged by the effects of random genetic drift and population isolation as a consequence of the influence of estuarine circulation on dispersal. In northern Fiordland, genetic structure approximated an isolation by distance model. However, the pattern in genetic differences suggests that distance alone cannot explain the most divergent populations and that fiord hydrography may increase the effect of genetic drift within populations in the fiords. Finally, our study indicates that populations within the fiords underwent recent rapid expansion, followed most probably by genetic drift due to a lack of gene flow among the fiords.


Assuntos
Variação Genética , Genética Populacional , Estrelas-do-Mar/genética , Movimentos da Água , Animais , Autorradiografia , Sequência de Bases , Primers do DNA , DNA Mitocondrial/genética , Água Doce , Geografia , Haplótipos/genética , Modelos Lineares , Dados de Sequência Molecular , Nova Zelândia , Polimorfismo Conformacional de Fita Simples , Dinâmica Populacional , Água do Mar , Análise de Sequência de DNA
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