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11.
Mauro Melo Júnior Catarina R. Marcolin Leonardo K. Miyashita Rubens M. Lopes 《Marine Ecology》2016,37(4):877-890
The inner shelf waters off Southeastern Brazil are periodically enriched by bottom intrusions of the cold and nutrient‐rich South Atlantic Central Water (SACW), which is transported offshore by the Brazil Current. This study examined the temporal contrasts in abundance and structure of pelagic copepod assemblages in a neritic station off Ubatuba, in relation to hydrography and phytoplankton biomass, to investigate the effects of SACW bottom intrusions on copepod population dynamics during three consecutive years. The water‐column characteristics shifted from a well‐mixed, more turbid and phytoplankton‐poor scenario during subsidence conditions to a stratified, less turbid and high Chl‐a concentration scenario during SACW bottom intrusions, leading to increased copepod diversity, abundance, and biomass. The rise in copepod diversity during SACW intrusions was related to the contribution of oceanic species in addition to coastal water species. The copepod community was numerically dominated by small‐sized species, such as Oncaea waldemari, Oithona plumifera, and clausocalanid and paracalanid copepodids, regardless of seasonality and SACW intrusions. Some large calanoid species contributed considerably to the total copepod biomass during intrusions. In addition to confirming that SACW seasonal intrusions play a key role in pelagic processes off Southeast Brazil, this study showed that the multiannual variability of SACW seasonal intrusions is important in regulating the structure and dynamics of copepod communities in this subtropical area. 相似文献
12.
Impact of trace metals on denitrification in estuarine sediments of the Douro River estuary,Portugal 总被引：1，自引：0，他引：1
Denitrification influences the nitrogen budget in estuaries by removing fixed nitrogen from the inorganic pool; rates are dependent on both geological and geographic conditions as well as increasing anthropogenic impacts. In this study the effects of copper (Cu), chromium (Cr), zinc (Zn), cadmium (Cd) and lead (Pb), on the denitrification pathway were evaluated in subtidal and intertidal sediments of the Douro River estuary. Dinitrogen, N2O and NO2− production rates were measured in triplicate slurries of field samples under different treatments of metal concentrations. Results demonstrated that similar metal amendments led to different site responses for denitrification, suggesting that variations in sediment properties (metal concentrations, grain size, organic matter content, etc.) and/or differences in denitrifying community tolerance modulate the level of metal toxicity. Denitrifying communities in subtidal muddy sediments were not affected by increasing concentrations of metals. In contrast, intertidal sandy sites revealed high sensitivity to almost all trace metals tested; almost complete inhibition by Cr (95%) and Cu (85%) was observed for 98 and 79 μg per gram of wet sediment respectively, and by Zn (92%) at the highest concentration added (490 μg per gram of wet sediment). Moreover, the addition of trace metals stimulated N2O and NO2− accumulation in intertidal sandy (Zn, Cu, Cr and Cd) and muddy sediments (Cu and Zn), demonstrating a pronounced inhibitory effect on specific steps within the denitrification enzymatic system. In summary, the results obtained suggest that, according to the type of estuarine sediment, trace metals cannot only reduce total N removal from an estuary via denitrification but also can enhance the release of N2O, a powerful greenhouse gas. 相似文献
13.
Inorganic nitrogen dynamics in intertidal rocky biofilms and sediments of the Douro River estuary (Portugal) 总被引：1，自引：0，他引：1
Catarina M. Magalhäes William J. Wiebe Samantha B. Joye Adriano A. Bordalo 《Estuaries and Coasts》2005,28(4):592-607
In this study rates of oxygen, ammonium (NH4
+), nitrate (NO3
−), nitrite (NO2
−), and nitrous oxide (N2O) fluxes, nitrogen (N) fixation, nitrification, and denitrification were compared between two intertidal sites for which
there is an abundant global literature, muddy and sandy sediments, and two sites representing the rocky intertidal zone where
biogeochemical processes have scarcely been investigated. In almost all sites oxygen production rates greatly exceeded oxygen
consumption rates. During daylight, NH4
+ and NO3
− uptake rates together with ammonification could supply the different N requirements of the primary producer communities at
all four sites; N assimilation by benthic or epilithic primary producers was the major process of dissolved inorganic nitrogen
(DIN) removal; N fixation, nitrification, and denitrification were minor processes in the overall light DIN cycle. At night,
distinct DIN cycling processes took place in the four environments, denitrification rates ranged from 9 ± 2 to 360 ± 30 μmol
N2 m−2 h−1, accounting for 10–48% of the water column NO3
− uptake; nitrification rates varied from 0 to 1712 ± 666 μmol NH4
+ m−2 h−1. A conceptual model of N cycle dynamics showed major differences between intertidal sediment and rocky sites in terms of
the mean rates of DIN net fluxes and the processes involved, with rocky biofilm showing generally higher fluxes. Of particular
significance, the intertidal rocky biofilms released 10 times the amount of N2O produced in intertidal sediments (up to 17 ± 6 μmol N2O m−2 h−1), representing the highest N2O release rates ever recorded for marine systems. The biogeochemical contributions of intertidal rocky substrata to estuarine
and coastal processes warrant future detailed investigation. 相似文献
14.
Spatial and temporal characterization of nutrient net uptake in a vegetated urban stream: Stream bank features leading to net uptake hotspots 
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下载免费PDF全文 Urban stream features can be used to promote nutrient retention; however, their interactions with different hydrological regimes impact nutrient cycling, decrease their retention capacity, and inhibit stream ecosystem functioning. This study analysed the temporal and spatial dynamics of the uptake of three nutrients (nitrate, ammonium, and phosphorus) in an urban drainage stream during high flows. In particular, we studied variations in net uptake along the right margin (with native vegetation and a roots mat) comparatively to the left margin (a non‐rooted grassy bank). Applying the spiralling approach within each subreach on either side, we determined nutrient subreach (sr) retention metrics: uptake rate coefficients , mass transfer rates , and areal uptake rates . Our results showed nitrate (NO3) and ammonium (NH4) net uptakes on the right side were higher and more frequent along subreaches where the root mat was more abundant ( [μg m?2 s?1] = 22.80 ± 1.13 for NO3 and 10.50 ± 0.81 for NH4), whereas on the left side both nutrients showed patchy and inconsistent net uptake patterns despite the homogeneous grass distribution. Net uptake for filtered reactive phosphorus (FRP) was not observed on either side at any flow rate. The impact of hydrological factors such as discharge, travel time, water depth, and concentration, on uptake metrics was studied. Despite increases in travel time as the flow decreased, there was a reduction in net uptake rates, and , on either side. This was attributed to a reduction in water level with declining flows, which decreased hydrologic connectivity with the stream banks, combined with a decrease in water velocity and a reduction in nutrient concentrations. We concluded the rooted bank acted as an effective retention area by systematically promoting net uptake resulting in a twofold increased dissolved inorganic nitrogen (DIN) retention relative to the non‐rooted side where net uptake was spatially localized and highly dynamic. Overall, this work emphasized the importance of strategically sampling close to biologically active surfaces to more accurately determine areas where gross uptake surpasses release process. 相似文献
15.
José Guerreiro Aldo Chircop Catarina Grilo Ana Viras Raquel Ribeiro Rudy van der Elst 《Marine Policy》2010
International conservation efforts and cooperation are increasingly necessary, particularly at an ecoregion level, for the achievement of international targets for protecting biodiversity and degradation of ecosystems. Whereas more than 11 percent of land is protected, less than 1 percent of marine space is similarly protected. Transboundary networks of marine protected areas and transboundary marine protected areas (TBMPAs) are an essential form of cooperation for meeting these international targets. This paper explores the diplomatic and political options for regional and sub-regional cooperation between Tanzania, Mozambique, and South Africa, for the establishment of transboundary conservation mechanisms in the Eastern African Marine Ecoregion (EAME). Five options for the establishment and management of these mechanisms are presented, together with actions to be taken to facilitate cooperation. The paper deal with a proposed strategy for the implementation of transboundary conservation mechanisms, focusing on TBMPAs, between the three countries at a biogeographical/sub-regional level, supported by lessons learnt in other transboundary marine conservation experiences. The paper concludes that although political will may exist among States sharing borders to establish TBMPAs, the complexity of dealing with sub-regional realities is a difficult obstacle to overcome in a single step. The situation at each border must be taken into account in order that different multi-scale and multivariate solutions, supported by a common baseline will ultimately converge in a common trilateral framework. Finally, a two-step approach seems to be in course with the declaration (October 2009) of a TBMPA linking Ponta do Ouro in Mozambique to iSimangaliso Wetland Park in South Africa, following one of the options formerly presented. 相似文献
16.
Impact of climate and hydrology on juvenile fish recruitment towards estuarine nursery grounds in the context of climate change 总被引：1，自引：0，他引：1
Catarina Vinagre Filipe Duarte Santos Henrique Nogueira Cabral Maria José Costa 《Estuarine, Coastal and Shelf Science》2009
Larvae of various coastal fish undergo immigration from spawning grounds towards estuarine nurseries. Several environmental factors can have an important impact on survival at this stage making it crucial for recruitment. Generalized linear models were applied in order to investigate the relation between river drainage, sea surface temperature (SST), NAO index and the North-South wind component intensity, over the two months prior to the estuarine colonization peak, and the densities of Platichthys flesus, Dicentrarchus labrax, Diplodus vulgaris and Diplodus bellottii in the nursery grounds based on a discontinuous historical dataset (from 1978 to 2006), for the Tagus estuary. The relation between SST over the 12 months prior to the estuarine colonization peak and fish densities in the nurseries was also investigated, as it integrates the periods of spawning stock maturation, spawning and larval immigration. While SST over the prior 12 months was negatively correlated with the abundance of P. flesus, it was positively correlated with the abundance of D. bellottii. Abundance of D. vulgaris was positively correlated with SST in the two months prior to the estuarine colonization peak, while the abundance of D. labrax was positively correlated with river drainage. The relations between SST and the abundance of P. flesus, a cold-water species with declining densities, and the subtropical species D. bellottii and D. vulgaris, which are increasing in abundance, are indicative of species abundance alterations related to climate warming. Dicentrarchus labrax will probably also be affected by climate change because of lowered precipitation and consequently river drainage. 相似文献
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Long-term changes in the production by estuarine macrobenthos affected by multiple stressors 总被引：1，自引：0，他引：1
M. Dolbeth P.G. Cardoso T.F. Grilo M.D. Bordalo D. Raffaelli M.A. Pardal 《Estuarine, Coastal and Shelf Science》2011
The macrobenthic production of an estuarine system was evaluated over a 14-year study period in a seagrass bed and in a sandflat. Over this period, the estuary suffered severe eutrophication and extreme weather events with important impacts on the community, impairing system functioning and ultimately the goods and services provided by the estuary (decline in the seagrass bed, decreased community production and/or a boost in the production by opportunist species, such as Hydrobia ulvae). Following the anthropogenic impacts, management measures were introduced which allowed a gradual recovery of the seagrass bed and a new macrobenthic community structure manifested by production increases of slow-growing species, such as Scrobicularia plana and Hediste diversicolor. There was a gradual re-orientation of energy into population biomass instead of population density but this was not translated into higher community production, mainly due to the decreased production of opportunist species (H. ulvae and several polychaetes). Several weather extreme events occurred during this post-mitigation phase - floods, heatwaves and droughts, all of which had negative impacts on macrobenthic dynamics and production. The heatwaves led to the greatest decreases in macrobenthic production, mainly due to S. plana perhaps associated with its physiological intolerance of higher temperatures. The prolonged drought that followed the heatwaves maintained low levels of production by S. plana and H. ulvae. With climate change, the frequency and intensity of extreme weather events are likely to increase worldwide so that the recovery of impacted/disturbed systems from impacts such as eutrophication may be seriously affected by these additional stressors, compromising attempts to improve the ecological quality of estuarine ecosystems. 相似文献
20.
Isabel Ribeiro da Costa Rita Fonseca Catarina Pinho Alexandre Araújo Luísa Catarina Martins Nuno Dias Ana Isabel Janeiro Guilherme Freitas 《Environmental Earth Sciences》2018,77(5):202
Draining through industrial areas of the Minas Gerais mining state (Brazil), some tributaries of the São Francisco River constitute a potential environmental hazard for this great river and threaten the quality of the regional soils for agriculture and other activities. Extensive geochemistry and mineralogy of sediments, soils and alluvial plains from six selected areas within the Consciência drainage basin close to an important Zn-extraction plant, have been carried out. In this report, detailed mineralogy of those samples and supporting geochemical data are discussed, taking into account their specific climactic and environmental context. Petrographic and electron microprobe characterization of the sand-grained fraction of these materials was complemented by XRD on their finer fraction: the main contaminant minerals are willemite (one of the Zn ores used in the industrial plant) and jarosite, though their contents are quite variable in the studied areas and also with depth; minor amounts of Zn-, Pb-, Cd-, and Mn-bearing mineral phases are also frequent, usually as inclusions in willemite or in polycrystalline clasts, or adsorbed on the finer materials, such as clay minerals and associated Fe-hydroxides. Mineralogical contamination is responsible for high metal contents in the soils and sediments of the areas closer to the plant (e.g. Zn ? 2000 mg kg?1 and Cd ? 20 mg kg?1, which are the Intervention Values for Industrial Areas) and the greatest contamination risks are related to the more labile phases that circulate throughout the alluvial plains, the shallow sediments and the stream bed. Monitoring the mineral/chemical contamination and its extent also constitutes a useful basis for future proposals to remediate and recover this industrial area in order to decrease medium- and long-term negative impacts of metal contamination on the local and downstream environments. 相似文献