Benthic foraminifera as proxies of marine influence in the Orosei marine caves,Sardinia, Italy

1. As a result of their location at the boundary between marine and continental domains, marine caves are affected by wide spatial and seasonal environmental changes. Only recently have benthic foraminifera been recognized as reliable indicators for the ecological zonation of these environments.
2. The present study is focused on two marine caves of the Orosei Gulf, Sardinia, Italy: Bue Marino and Bel Torrente. It investigates the spatial and seasonal variability of benthic foraminiferal assemblages relative to sediment grain size and water parameters (temperature, salinity, pH, and dissolved oxygen) collected during two campaigns in August 2014 and April 2015. The results from 2014 have been partially published.
3. Based on a comparison of the results of the two campaigns, the considerable reduction of foraminiferal abundance in Bel Torrente was deduced to occur because of the strong freshwater flows occurring during the rainy season; in Bue Marino, the less severe water flow allowed the identification of both living and dead foraminifera, although strongly reduced in number. These identifications allowed benthic foraminifera to be used to define the ecological zonation.
4. Entrance, confluence, and transitional ecozones were identified in Bue Marino cave on the basis of species abundance. The second ecozone, not recognized in 2014, was correlated with plant debris at the confluence of the two cave branches. The other two ecozones, which are characterized by the faunal shift from hyaline‐ to agglutinated‐prevalent assemblages, were attributed to the gradient of abiotic parameters detected from the outer to the inner portions of the cave. In both campaigns the same ecozones were recognized in terms of species composition, with exceptions being found to different extents as a result of seasonal variability.
5. As the distribution of foraminiferal ecozones is conditioned by a decreasing gradient of marine influence, long‐term monitoring may be regarded as a promising tool for future studies on sea‐level change.

     

Stream bed organic carbon and biotic integrity

• 1. Allochthonous carbon is the basis of the detrital food web in low‐order, warmwater stream ecosystems, and stream‐bed sediments typically function as carbon reservoirs. Many of the same factors that govern carbon input and storage to streams (e.g. riparian vegetation, large wood, heterogeneous boundaries) have also been identified as key attributes of stream fish habitat.
• 2. Effects of channel incision on sand‐bed stream carbon reservoirs and indices of biological integrity (IBIs) based on fish collections were examined for four streams exhibiting a range of incisement in northern Mississippi. Observed mean C concentrations (mass percentage) ranged from 0.24±0.36% for a non‐incised stream to only 0.01±0.02% for a severely incised channel, and were not correlated with large wood (LW) density, perhaps because LW density at one site was elevated by a habitat rehabilitation project and at another site by accelerated inputs from incision‐related riparian tree fall. Fish IBI was positively correlated with bed C (r=0.70, p=0.003), and IBIs for reference streams were more than 50% greater than those computed for the most severely degraded sites.
• 3. More testing is needed to determine the efficacy of stream bed C as an indicator, but its importance to warmwater stream ecosystems, and the importance of covarying physical and hydrologic conditions seems evident.

Published in 2008 by John Wiley & Sons, Ltd.     

基于高精度声学图像的海洋牧场海床类型识别

人工鱼礁作为海洋牧场建设的基础生态工程,在海洋生态环境修复和渔业资源增殖方面起着重要作用。随着人工鱼礁的大量投放,海洋牧场海床逐步转变为高度异质性的底栖生境,底栖生态变化会直接影响到底栖及底层生物的栖息与繁衍。针对传统调查方法在海洋牧场中的局限性,聚焦天津海洋牧场,基于侧扫声纳后散射数据和多波束测深数据,从侧扫图像亮度、图像纹理及地形起伏度等3个维度,探索了天津海洋牧场海床类型识别、分类和面积量化的新方法。研究表明,天津海洋牧场共发现人工鱼礁、牡蛎类、淤泥类、蛤仔泥混类、牡蛎泥混类及碎贝泥混类等6种海床类型,基于声学图像特征的海床类型识别方法准确率达90%,可满足海洋牧场底栖生态研究的需求;通过对比分析,天津海洋牧场本底淤泥类海床消退为58.19%,贝类海床增至7.96%,贝类资源增殖效果明显;人工鱼礁周边新生牡蛎礁0.246 km2,并伴有0.303 km2的牡蛎泥混海床待发育为牡蛎礁,海洋牧场建设对牡蛎礁具有重要的修复作用。本研究探索了适宜于海洋牧场的海床声学分类方法,探讨了声学技术对传统底栖调查方法的补充与完善作用,明确了海床类型与声学图像特征的紧密联系,验证了海洋牧场对牡蛎礁的修复作用,成果可有效应用于近岸海域生境修复、贝类资源量精准评估及牡蛎礁演化机理等领域的研究。     

Spatial correspondence between areas of concentration of Patagonian scallop (Zygochlamys patagonica) and frontal systems in the southwestern Atlantic

It has been hypothesized that the geographical location of scallop beds in extensive shelf regions mirrors hydrographic structures (e.g. frontal systems) that favor the retention/concentration of pelagic larvae. Large, discontinuous concentrations of the Patagonian scallop (Zygochlamys patagonica) are known to have occurred recurrently (for more than 30 yr) at certain geographical locations over the extensive Patagonian shelf. These stocks, exploited since 1996, currently support one of the most important scallop fisheries in the world. Here, we investigate whether those aggregations are spatially coincidental with major frontal systems. Several pieces of information were used: historical survey data documenting the geographic distribution of the Patagonian scallop beds, catch and effort data from the commercial fleet, oceanographic data on frontal systems, and remote sensing imagery. We found that large-scale aggregations do match the location of three major and very different frontal systems in the southwestern Atlantic: the Shelf-Break Frontal System, the Northern Patagonia Frontal System, and the Southern Patagonia Frontal System. We describe the three frontal systems and their associated scallops fishing grounds and discuss which processes can contribute to sustaining the productivity of the scallop grounds in each case.     

The effect of the sampling scale on zooplankton community assessment and its implications for the conservation of temporary ponds in south‐west Spain

• 1. The zooplankton (rotifer and microcrustacean) assemblages of temporary ponds in the Doñana National Park (south‐west Spain) have been compared in two surveys of contrasting scales that resulted in the same number of samples: an extensive survey of 36 ponds sampled in May 1998 (or widespread survey) and a survey of nine ponds sampled four times over 2 years (or cumulative survey).
• 2. The total number of microcrustacean and rotifer taxa was larger in the cumulative survey (43 and 41 taxa, respectively) than in the widespread survey (39 and 34, respectively). Crustacean assemblages became less alike throughout the cumulative survey.
• 3. The presence of invertebrates (Coleoptera, Odonata, Heteroptera and crayfish) and aquatic vertebrates (fish and salamanders) was recorded as an estimate of potential predator impact on zooplankton. Several pond features (water depth, conductivity, pH, chlorophyll a concentration, distance to the nearest permanent pond and to the marsh) were also measured in both surveys.
• 4. A combination of these environmental factors was more strongly related to the similarity matrices derived from the zooplankton assemblages of the cumulative survey (Rho=0.7) than to those of the widespread survey (Rho<0.4). The distance of ponds to the marsh was an important factor in explaining this correlation as well as the strongest factor in the ordination of crustacean assemblages following a CCA.
• 5. Predation by exotic fish in long‐hydroperiod ponds where overflow drains to the nearby marsh (fish source) is the mechanism likely to explain the changes in crustacean composition recorded in the cumulative survey.
• 6. The cumulative survey was more suitable for the study of zooplankton diversity as it rendered a higher number of taxa and gave more insight into the mechanisms that explain taxon richness. Thus, conservation strategies in temporary habitats require a scale of observation that includes long temporal changes.

Copyright © 2006 John Wiley & Sons, Ltd.     

Benthic habitat modelling and mapping as a conservation tool for marine protected areas: A seamount in the western Mediterranean

1. An ecologically representative, well‐connected, and effectively managed system of marine protected areas (MPAs) has positive ecological and environmental effects as well as social and economic benefits. Although progress in expanding the coverage of MPAs has been made, the application of management tools has not yet been implemented in most of these areas.
2. In this work, distribution models were applied to nine benthic habitats on a Mediterranean seamount within an MPA for conservation purposes. Benthic habitat occurrences were identified from 55 remotely operated vehicle (ROV) transects, at depths from 76 to 700 m, and data derived from multibeam bathymetry. Generalized additive models (GAMs) were applied to link the presence of each benthic habitat to local environmental proxies (depth, slope, backscatter, aspect, and bathymetric position index, BPI).
3. The main environmental drivers of habitat distribution were depth, slope, and BPI. Based on this result, five different geomorphological areas were distinguished. A full coverage map indicating the potential benthic habitat distribution on the seamount was obtained to inform spatial management.
4. The distribution of those habitats identified as vulnerable marine ecosystems (VMEs) was used to make recommendations on zonation for developing the management plan of the MPA. This process reveals itself as an appropriate methodological approach that can be developed in other areas of the Natura 2000 marine network.

     

Macrophytes promote aquatic insect conservation in artificial ponds

1. Farmland ponds promote regional aquatic biodiversity; however, optimally managing these ponds requires knowledge on how the biodiversity differs between ponds across catchments with different land uses.
2. This study investigated the response of macrophytes, both those in the pond and on the bank, as well as dragonfly and water beetle species richness, diversity and composition in artificial ponds, to numerous environmental variables in catchments dominated by three land uses: protected areas (as reference sites), sugarcane‐dominated and forestry‐dominated landscapes, across two seasons.
3. There was a strong association between insect species richness and vegetation cover, particularly sedges (Cyperus spp.) in spring and bulrushes (Typha capensis) in summer. There was also a positive response between insect species richness and sedges up to 70% cover, and bulrushes up to 40% cover, after which there was a decrease. Furthermore, the protected area ponds contained more rare and specialist insect species. Pond size was not a major variable for biodiversity overall.
4. Although there was generally little congruence in composition among the three taxa, dragonflies were a good surrogate for water beetles and floating macrophytes.
5. Well‐vegetated ponds, both in the water and along the margin, are the most suited to promoting biodiversity, as long as the vegetation is not too dense, and not dominated by one plant species.
6. Artificial ponds in production landscapes have great potential for conserving aquatic species, irrespective of land use, as long as there is management for macrophyte density and heterogeneity.

     

Taxonomic and geographical representation of freshwater environmental DNA research in aquatic conservation

1. Freshwater macro‐organismic environmental DNA (eDNA) is gaining increasing popularity in detecting invasive species, assessing community assemblages, and in mapping the distribution of taxa that are rare or otherwise difficult to monitor. The objectives of this article are to review the targets of published freshwater eDNA research in relation to aquatic conservation with a focus on geographic regions covered, as well as the habitats and species investigated.
2. The analysis of 272 peer‐reviewed articles published between 2005 and 2018 revealed that 57% of the 238 primary research papers have a focus on conservation science, mostly addressing invasive and endangered species, followed by 23% papers investigating methodological developments and 11% biodiversity surveys also using eDNA metabarcoding. A strong geographical pattern emerged, with Africa, South America, and the tropics being under‐represented. Taxonomic coverage was dominated by 123 fish species, followed by 29 amphibian and 28 mollusc species. Freshwater arthropods (27 taxa) were under‐represented in relation to their estimated species richness.
3. Taxonomic bias towards certain species such as fishes observed in freshwater eDNA research is pervasive in biodiversity research and conservation sciences, and thus is not surprising. Geographical representation was biased, with a few industrialized countries from the Northern Hemisphere contributing 72% of the studies. Both findings parallel biases known from other research areas, such as marine eDNA analysis, taxonomy, or invasion biology.
4. The application of eDNA in freshwater conservation will benefit from the development of general standards and guidelines that are necessary to integrate freshwater macrobial eDNA techniques in existing monitoring frameworks. To aid future freshwater conservation, our suggestions are to harmonize eDNA methods for comparable and easier implementation worldwide, and to increase international cooperation and funding for under‐represented geographical regions and neglected taxa. This is especially crucial for the known biodiversity hotspots in developing countries where rapid changes occur to freshwater habitats and biodiversity.

     

Trophic fingerprint of fish communities in subtropical floodplain lakes

Stable nitrogen isotope ratios (δ¹⁵N) and gut content analysis are commonly used to detect trophic relationships in aquatic systems. Nonetheless, the use of δ¹⁵N in determining the suitability of quantitative and qualitative dietary data as representations of trophic relationships in lake ecosystems remains unverified. Quantitative and qualitative dietary data on 46 fish species were obtained from field surveys in the floodplain lakes of the Yangtze Plain to calculate trophic position and benthivory. Dietary measures using the stable isotope approach were validated. The dietary approach yields comparable results in detecting trophic relationships in lake ecosystems. Our estimation of the benthivory of the 46 fish species ranged from 1.5% to 100%, with an average of 60.3%. These figures support the assumption that benthic energy pathways account for more than half of total fish consumption. Our feeding guild data confirm that more than 50% (including 25 species) of the studied fish species in the floodplain lakes of the Yangtze Plain are omnivorous, suggesting that omnivory is prevalent among subtropical floodplain lakes.     

Differences in stable isotope ratios of Dall’s porpoises (Phocoenoides dalli) between coastal and oceanic areas of the North Pacific

Carbon and nitrogen stable isotope ratios in the muscle of Dall’s porpoises were measured. Samples were collected from the catches of the hand harpoon fishery, incidental catches of drift net, and scientific research on the use of drift nets. Samples were from the North Pacific, Sea of Japan, Sea of Okhotsk, and Bering Sea. Although no variation in δ¹⁵N was observed, δ¹³C was significantly different between population groups near Japan and the oceanic North Pacific and Bering Sea. The difference may be due not only to local variation in prey species, but also to an overall difference in carbon stable isotope ratios that originate from coastal benthic or oceanic pelagic‐based food webs. We differentiated Dall’s porpoise population groups from both areas using carbon stable isotope ratios with an error rate of <5%. Although further study is needed, our results suggest that carbon stable isotope ratios could possibly be an indicator of whether a Dall’s porpoise belongs to a coastal benthic or oceanic pelagic food web.