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Díaz-Almela E Marbà N Alvarez E Santiago R Holmer M Grau A Mirto S Danovaro R Petrou A Argyrou M Karakassis I Duarte CM 《Marine pollution bulletin》2008,56(7):1332-1342
Fish farms represent a growing source of anthropogenic disturbance to benthic communities, and efficient predictors of such impacts are urgently needed. We explored the effects of fish farm benthic organic and nutrient inputs on the population dynamics of a key seagrass species (Posidonia oceanica) in four Mediterranean deep meadows adjacent to sea bream and sea bass farms. We performed two annual plant censuses on permanent plots at increasing distance from farms and measured benthic sedimentation rates around plots. High shoot mortality rates were recorded near the cages, up to 20 times greater than at control sites. Recruitment rates increased in variability but could not compensate mortality, leading to rapid seagrass decline within the first 100 m from cages. Seagrass mortality increased with total sedimentation rates (K=0.55, p<0.0002), and with organic matter (K=0.50, p=0.001), total nitrogen (K=0.46, p=0.002) and total phosphorus (K=0.56, p<3.10(-5)) inputs. P. oceanica decline accelerated above a phosphorus loading threshold of 50mg m(-2)day(-1). Phosphorus benthic sedimentation rate seems a powerful predictor of seagrass mortality from fish farming. Coupling direct measurements of benthic sedimentation rates with dynamics of key benthic species is proposed as an efficient strategy to predict fish farm impacts to benthic communities. 相似文献
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The light-limitation hypothesis was tested to assess whether water turbidity had caused the decline of a Mediterranean Posidonia oceanica (L.) Delile meadow in an area affected by a harbor. The annual growth, photosynthesis and rhizome starch concentrations of seagrass were measured and related to changes in light availability and dissolved nutrient concentration along a gradient of meadow degradation from areas close to the harbor outwards. Environmental and plant variables were measured in three stations placed along this gradient and compared with a reference station at an undisturbed meadow. The light attenuation coefficient (k) increased toward the inner harbor area, mainly due to sediment resuspension. The shoot density and leaf productivity of P. oceanica shoots were much lower in disturbed stations of the inner harbor area than in the outer, less disturbed station and the reference meadow. However, daily leaf carbon gains, calculated from the photosynthetic rates at saturating irradiance (Pmax) and the daily period in which seagrass receives light higher than its saturating irradiance (Hsat), suggested positive C-balance in all stations. This was partly explained by photo-acclimatization of seagrass to the reduced light availability at the disturbed harbor stations (inner and intermediate), as indicated by the lengthening of Hsat and the decrease in saturating irradiance (Isat) and respiratory demands. Despite photo-acclimatization, disturbed harbor stations showed less positive C-balance, seen not only in their lower leaf growth and biomass but also in a decrease in rhizome carbohydrate reserves (starch). Our results suggest that light reduction account for the reduced seagrass productivity and abundance. However, meadow decline (in terms of shoot mortality) in the harbor area is well above that predicted from similar light environments of nearby meadows or simulated in shading experiments. Thus, there are other factors than light limitation involved in seagrass mortality, most probably through more complex interactions (e.g. nutrient-epiphytes-grazers, water quality––siltation). 相似文献
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Holmer M Argyrou M Dalsgaard T Danovaro R Diaz-Almela E Duarte CM Frederiksen M Grau A Karakassis I Marbà N Mirto S Pérez M Pusceddu A Tsapakis M 《Marine pollution bulletin》2008,56(9):1618-1629
This paper provides a synthesis of the EU project MedVeg addressing the fate of nutrients released from fish farming in the Mediterranean with particular focus on the endemic seagrass Posidonia oceanica habitat. The objectives were to identify the main drivers of seagrass decline linked to fish farming and to provide sensitive indicators of environmental change, which can be used for monitoring purposes. The sedimentation of waste particles in the farm vicinities emerges as the main driver of benthic deterioration, such as accumulation of organic matter, sediment anoxia as well as seagrass decline. The effects of fish farming on P. oceanica meadows are diverse and complex and detected through various metrics and indicators. A safety distance of 400 m is suggested for management of P. oceanica near fish farms followed by establishment of permanent seagrass plots revisited annually for monitoring the health of the meadows. 相似文献
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Eight shallow water Posidonia oceanica meadows were sampled in June 1999 along 300 km of the Ligurian coast and were compared through shoot density and lepidochronology. The growth of the seagrass was examined in the light of climate fluctuations and local stresses, colonisation by alien, invasive alga Caulerpa taxifolia, and effects of the oil spill from the tanker "Haven", and other anthropogenic impacts. Both shoot density and lepidochronology pointed to a generalised state of regression of all the meadows. The analysis of long-term growth curves of the rhizomes showed a positive trend parallel to the increase of air temperature. Two main groups of meadows were individuated on the basis of growth curve similarity. The first included four meadows, namely Ventimiglia, Imperia, Noli and Prelo, that were characterised by average values of rhizome growth of 8-9.1 mmyear(-1) and shoot density greater than 200 shootsm(-2). Although the Imperia meadow was the only one where the alien invasive alga C. taxifolia was found, it did not show differences for rhizome growth in comparison to the other meadows. The second group was formed by meadows that had suffered past anthropogenic impacts: Arenzano and Monterosso al Mare. They showed higher rhizome growth rates (9.4-10.6 mmyear(-1)) and shoot densities between 200 and 100 shootsm(-2). At Arenzano, where "Haven" oil was stranded in April 1991, no rhizome older than 8 years was found, thus confirming the shoot mortality induced by the oil spill event. The two last meadows exhibited growth curves very different from all the others: Portovenere, is a shallow meadow where P. oceanica merely survives in an extremely degraded situation with highest rhizome growth rate (12 mmyear(-1)), the other, Riva Trigoso, is the only meadow implanted on rock and had the lowest growth rates (7.1 mm year(-1)). 相似文献
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Marine fish farming is increasing rapidly in the Mediterranean and in contrast to the Atlantic the coastal zone in the Mediterranean is characterized by clear waters with high transparency. This allows benthic primary producers such as the slow-growing seagrass Posidonia oceanica to grow at large depths at locations suitable for fish farming and generating a conflict between the conservation of these meadows and the growth of aquaculture operations in the Mediterranean. In this paper we review the current knowledge on environmental interactions between fish farming and benthic primary producers with particular focus on P. oceanica, as this seagrass is a key component along Mediterranean coasts. The recovery times of P. oceanica are very long, in the order of centuries, and losses of this species are thus considered to be irreversible at managerial time scales. 相似文献
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Como S Magni P Casu D Floris A Giordani G Natale S Fenzi GA Signa G De Falco G 《Marine pollution bulletin》2007,54(6):733-744
We studied the spatial variability and within-year temporal changes in hydrological features, grain size composition and chemical characteristics of sediments, as well as macrofaunal assemblages, along a heavily modified inlet in the Gulf of Oristano (western Sardinia, Italy). The inlet connects the Cabras lagoon to the gulf through a series of convoluted creeks and man-made structures, including a dam and fish barriers built in the last three decades. Sediments were muddy and mainly composed of the "non-sortable" fraction (i.e., <8 microm particle size) in all four areas investigated: Lagoon, Creeks, Channel and Seaward. Along the inlet, however, the ratio between the <8 microm and the 8-64 microm fractions was highest in Creeks and Channel, between the fish barriers and the dam, suggesting impaired hydrodynamics. Consistently, steep gradients in water salinity, temperature and dissolved oxygen concentrations were found in proximity to the fish barriers. The whole inlet was characterized by a major organic enrichment of sediments, with up to an annual mean of 33.6% of organic matter and 11.7% of total organic carbon in Seaward due to the presence of seagrass leaf litter. Acid-volatile sulphide and chromium-reduced sulphur concentrations were highest throughout the year in Seaward and Lagoon, respectively, with a peak in summer. Consistently, the whole inlet supported low structured macrofaunal assemblages dominated by few opportunist species, with a relatively lower diversity in Lagoon throughout the year and the highest abundances in Seaward in summer. We infer that the presence of artificial structures along the inlet, such as fish barriers and the dam, impair the lagoon-gulf hydrodynamics, sediment exchange and animal recruitment and colonization. We suggest that the removal of these structures would favour water renewal in the Cabras lagoon, but would also increase the outflow of organic C-bonding fine particles into the gulf with serious consequences for Posidonia oceanica and Cymodocea nodosa seagrass meadows. We conclude that all possible consequences of such initiatives should be carefully considered before any action is taken. 相似文献
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SongLin Liu ZhiJian Jiang YiQin Deng YunChao Wu ChunYu Zhao JingPing Zhang Yuan Shen XiaoPing Huang 《中国科学:地球科学(英文版)》2017,60(12):2108-2117
Seagrass leaf litters are an important source of sediment organic carbon (SOC). However, the mechanisms of seagrass leaf litter decomposition influencing SOC composition and the key transformation processes remain unknown. We performed a laboratory chamber experiment to compare the labile organic carbon (OC) composition and the enzyme activities governing SOC transformation between the seagrass group (seagrass leaf litter addition) and the control group. The results showed that the seagrass leaf litter decomposition significantly elevated the salt-extractable carbon (SEC) content and the SEC/SOC. Additionally, the levels of invertase, polyphenol oxidase, and cellulase in the seagrass leaf litters addition group were generally higher than in the control group, which could elevate recalcitrant OC decomposition. Following 24 days incubation, addition of seagrass leaf litter increased the amount of CO2 released, but decreased the SOC content. Therefore, seagrass leaf litter decomposition leached abundant dissolved OC, which enhanced the activity and transformation of SOC. 相似文献
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Paolo Tomassetti Emma Persia Isabel Mercatali Danilo Vani Veronica Marussso Salvatore Porrello 《Marine pollution bulletin》2009,58(4):533-541
The effects of solid organic wastes from a marine fish farm on sediment was tested using macrobenthic fauna as biological indicators. Impact on benthic fauna was evaluated in the vicinity of a fish farm in the Tyrrhenian Sea (Western Mediterranean) between July 2001 and October 2002. Changes in benthic community structure were investigated using multivariate, distributional and univariate analyses (diversity indices, AMBI and M-AMBI). The results showed sharp disturbance of assemblages under the cages and no effects in the area more than 25 m from the cages. Sediment alterations were related to an increase in farmed biomass and its wastes, as well as to low current speed that allowed accumulation of organic matter on the sea floor. It was possible to follow the ecological succession from slightly altered assemblages to heavily polluted ones in the very short period of a single fish fattening cycle (15 months). 相似文献
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Ecosystem carbon stocks across a tropical intertidal habitat mosaic of mangrove forest,seagrass meadow,mudflat and sandbar 
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下载免费PDF全文 Intertidal habitats provide numerous ecosystem services, including the sequestration and storage of carbon, a topic of great recent interest owing to land‐cover transitions and climate change. Mangrove forests and seagrass meadows form a continuum of intertidal habitats, alongside unvegetated mudflats and sandbars, however, studies that consider carbon stocks across these spatially‐linked, threatened ecosystems are limited world‐wide. This paper presents the results of a field‐based carbon stock assessment of aboveground, belowground and sediment organic carbon stock to a depth of 1 m at Chek Jawa, Singapore. It is the first study of ecosystem carbon stocks of both vegetated and unvegetated intertidal habitats in the tropics. Ecosystem carbon stocks were 497 Mg C ha‐1 in the mangrove forest and 138 Mg C ha‐1 in the seagrass meadow. Sediment organic carbon stock dominated the total storage in both habitats, constituting 62% and >99% in the mangrove forest and seagrass meadow, respectively. In the adjacent mudflat and sandbars, which had no vegetative components, sediment organic carbon stock ranged from 124–143 Mg C ha‐1, suggesting that unvegetated habitats have a carbon storage role on the same order of importance as seagrass meadows. This study reinforces the importance of sediment in carbon storage within the intertidal ecosystem, and demonstrates the need to consider unvegetated habitats in intertidal ‘blue carbon’ stock assessments. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
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通过对鱼苗时期鄱阳湖网箱养殖区沉积物、饵料及鱼粪等样品总有机碳(TOC)含量、总氮(TN)含量、碳氮比(C/N)、δ^13 C及δ^15 N的测定,分析探讨了鄱阳湖网箱养殖区沉积物有机质来源,量化了网箱养殖废物对养殖区沉积物有机质的贡献.结果表明,网箱养殖区沉积物的δ^13 C和δ^15 N值分别为-27.67‰~-25.65‰和5.19‰~7.27‰,饵料的δ^13 C和δ^15 N值分别为-24.73‰和10.28‰,鱼粪的δ^13 C和δ^15 N值分别为-26.30‰和15.54‰.网箱养殖区沉积物有机质来源主要有残饵、浮游生物及其他来源,其贡献率分别为48.3%±11.4%、25.6%±11.3%及26.0%±5.8%,而鱼粪的贡献几乎可以忽略不计.在水动力平流引起的扩散及沉积物的再悬浮的影响下,网箱养殖源有机质的扩散距离达1500 m.在鱼苗时期,鱼类网箱养殖的残饵是鄱阳湖网箱养殖区沉积物有机质的主要来源. 相似文献
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Rotation of cages within fish farm leases and the subsequent fallowing of areas of seabed is commonly used to allow recovery of infaunal communities following periods of organic enrichment. To investigate the effect of different background environmental conditions on recovery response, two Atlantic salmon (Salmo salar) fish farm sites in southeast Tasmania were sampled over two commercial fallowing cycles. Despite similar stocking levels and feed input there were significant differences in the way in which sediment at each farm responded to the cessation of fish stocking. Sediments at both farms showed some improvement in the community structure over a three month fallow period, but the community structure only recovered to that present before stocking not to that at the reference sites. The similarity of the impact sites to the reference sites increased from ca. 25% to 31% at one site and 11% to 27% at the other after fallowing. Rate and extent of recovery were affected by farm location, initial impact of the sediments, and length of fallow period. Initial recovery was faster at the more sheltered site than at the more exposed site, possibly reflecting differences in environmental resilience with the more sheltered location better able to assimilate organic inputs. Accordingly general fallowing management protocols may need to be adapted to reflect differences between sites. The findings of this study suggest that the recovery response of benthic communities can be predicted once baseline conditions are understood. 相似文献
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The present study aimed to establish potential indicators of fish farming pollution in muddy substrate, by means of meiofauna, and to test whether the effect of the fish farm is more important to determine the meiofauna community than the seasonal environmental conditions. Sampling was performed in spring, after several months of light feeding, and in summer, at high food supply. Samples were collected in three directions at various distances from the floating cages. Harpacticoid copepods and kinorhynchs, whose abundance decreased under the cages, were put forward as indicator taxa. However, harpacticoid copepods were sensitive to fish farm only, while kinorhynchs showed responsiveness to fish farm and to seasonal environmental conditions. Total meiofauna density was dependent on season sensu stricto. The nMDS clearly showed a ‘cage community’ and ‘control community’ in both sampling occasions; therefore it is a good tool for impact assessment. 相似文献
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A large-scale, manipulative experiment was conducted to examine the extent and rate of recovery of meadows of the temperate Australian seagrass, Amphibolis griffithii to different light-reduction scenarios typical of dredging operations, and to identify potential indicators of recovery from light reduction stress. Shade cloth was used to mimic different intensities, durations and start times of light reduction, and then was removed to assess the recovery. The meadow could recover from 3 months of light stress (5-18% ambient) following 10 months re-exposure to ambient light, even when up to 72% of leaf biomass was lost, much faster recovery rates than has previously been observed for large seagrasses. However, when the meadow had been shaded for 6-9 months and more than 82% of leaf biomass was lost, no recovery was detected up to 23 months after the light stress had ceased, consistent with other studies. Five potential indicators of recovery were recommended. 相似文献
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Lucia S. Herbeck Miriam Sollich Daniela Unger Marianne Holmer Tim C. Jennerjahn 《Marine pollution bulletin》2014
The impact of pond aquaculture effluents on the distribution and performance of seagrasses was examined in NE Hainan, tropical China. Samples were taken along transects in three back-reef areas with different extent of aquaculture production in their hinterland. High δ15N in seagrass leaves and epiphytes (6–9‰) similar to values in pond effluents documented aquaculture as dominant nitrogen source in the back-reefs with decreasing impact with distance from shore. Seagrass species abundance, shoot density and biomass were lower and concentrations of nutrients, chlorophyll and suspended matter were higher at nearshore sites with high and moderate pond abundance than at the control site. High epiphyte loads and low δ34S in seagrass leaves suggest temporal shading and sulphide poisoning of the nearshore seagrasses. Observed gradients in environmental parameters and seagrass performance indicate that the distance from the pond outlets and size of the adjacent pond agglomeration are major determinants of seagrass degradation. 相似文献
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Seagrass population dynamics and water quality in the Great Barrier Reef region: a review and future research directions 总被引：6，自引：0，他引：6
Seagrasses in the Great Barrier Reef region, particularly in coastal habitats, act as a buffer between catchment inputs and reef communities and are important habitat for fisheries and a food source for dugong and green turtle. Within the Great Barrier Reef region there are four different seagrass habitat types now recognised. The spatial and temporal dynamics of the different types of seagrass habitat is poorly understood. In general seagrass growth is limited by light, disturbance and nutrient supply, and changes to any or all of these limiting factors may cause seagrass decline. The capacity of seagrasses to recover requires either recruitment via seeds or through vegetative growth. The ability of seagrass meadows to recover from large scale loss of seagrass cover observed during major events such as cyclones or due to anthropogenic disturbances such as dredging will usually require regeneration from seed bank. Limited research into the role of pollutants on seagrass survival suggests there may be ongoing impacts due to herbicides, pesticides and other chemical contaminants. Further research and monitoring of seagrass meadow dynamics and the influence of changing water quality on these is needed to enhance our ability to manage seagrasses on the Great Barrier Reef. 相似文献
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Global sensitivity analysis is a useful tool to understand process‐based ecosystem models by identifying key parameters and processes controlling model predictions. This study reported a comprehensive global sensitivity analysis for DRAINMOD‐FOREST, an integrated model for simulating water, carbon (C), and nitrogen (N) cycles and plant growth in lowland forests. The analysis was carried out for multiple long‐term model predictions of hydrology, biogeochemistry, and plant growth. Results showed that long‐term mean hydrological predictions were highly sensitive to several key plant physiological parameters. Long‐term mean annual soil organic C content and mineralization rate were mainly controlled by temperature‐related parameters for soil organic matter decomposition. Mean annual forest productivity and N uptake were found to be mainly dependent upon plant production‐related parameters, including canopy quantum use efficiency and carbon use efficiency. Mean annual nitrate loss was highly sensitive to parameters controlling both hydrology and plant production, while mean annual dissolved organic nitrogen loss was controlled by parameters associated with its production and physical sorption. Parameters controlling forest production, C allocation, and specific leaf area highly affected long‐term mean annual leaf area. Results of this study could help minimize the efforts needed for calibrating DRAINMOD‐FOREST. Meanwhile, this study demonstrates the critical role of plants in regulating water, C, and N cycles in forest ecosystems and highlights the necessity of incorporating a dynamic plant growth model for comprehensively simulating hydrological and biogeochemical processes. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
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Qiuying Han Laura M. Soissons Dongyan Liu Marieke M. van Katwijk Tjeerd J. Bouma 《Marine pollution bulletin》2017,114(1):201-209
A manipulative field experiment was designed to investigate the effects of sediment-nutrients and sediment-organic matters on seagrasses, Zostera japonica, using individual and population indicators. The results showed that seagrasses quickly responded to sediment-nutrient and organic matter loading. That is, sediment-nutrients positively impacted on seagrasses by increasing N content of leaves and roots, leaf length and belowground biomass. Sediment-organic matter loading lowered N content of seagrass leaves and belowground biomass. Negative effects of organic matter loading were aggravated during nutrient loading, by decreasing N content of leaves, P content of roots, leaf width, shoot number in the middle period of the experiment, increasing C/N ratio of leaves, C/P and N/P ratio of roots and above to belowground biomass ratio of seagrasses. Consequently, Z. japonica could be considered as a fast indicator to monitor seagrass ecosystem status in the eutrophic areas and facilitate to interpreting the response of seagrasses to multiple stressors. 相似文献
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Despite marked gradients in nutrient availability that control the abundance and species composition of seagrasses in south Florida, and the importance of nutrient availability in controlling abundance and composition of epiphytes on seagrasses in other locations, we did not find that epiphyte load on the dominant seagrass, Thalassia testudinum, or that the relative contribution of algal epiphytes to the epiphyte community, was positively correlated with nutrient availability in the water column or the sediment in oligotrophic seagrass beds. Further, the abundance of microphytobenthos, as indicated by Chlorophyll-a concentration in the sediments, was not directly correlated with concentrations of nutrients in the sediments. Our results suggest that epiphyte and microphytobenthos abundance are not unambiguous indicators of nutrient availability in relatively pristine seagrass environments, and therefore would make poor candidates for indicators of the status and trends of seagrass ecosystems in relatively low-nutrient environments like the Florida Keys. 相似文献