Abundance Of Sensitive Species Research Articles

Threshold Responses in the Taxonomic and Functional Structure of Fish Assemblages to Land Use and Water Quality: A Case Study from the Taizi River

Biological functional traits help to understand specific stressors that are ignored in taxonomic data analysis. A combination of biological functional traits and taxonomic data is helpful in determining specific stressors which are of significance for fish conservation and river basin management. In the current study, the Taizi River was used as a case study to understand the relationships between the taxonomic and functional structure of fish and land use and water quality, in addition to determining the thresholds of these stressors. The results showed that taxonomic structure was significantly affected by the proportion of urban land and specific conductivity levels, while functional metrics were influenced by the proportions of farmland and forest. Threshold indicator taxa analysis found that Phoxinus lagowskii, Barbatula barbatula nuda, Odontobutis obscura, and Cobitis granoei had negative threshold responses along the gradients of urban developments and specific conductivity. There was a significant change in fish taxonomic composition when the proportion of urban land exceeded a threshold of 2.6–3.1%, or specific conductivity exceeded a threshold of 369.5–484.5 μS/cm. Three functional features—habitat preference, tolerance to disturbances, and spawning traits—showed threshold responses to the proportion of farmland and forest. The abundance of sensitive species should be monitored as part of watershed management, as sensitive species exhibit an earlier and stronger response to stressors than other functional metrics. Sensitive species had a positive threshold response to the proportion of forest at 80.1%. These species exhibited a negative threshold response to the proportion of farmland at 13.3%. The results of the current study suggest that the taxonomic and functional structure of fish assemblages are affected by land use and water quality. These parameters should be integrated into routine monitoring for fish conservation and river basin management in the Taizi River. In addition, corresponding measures for improving river habitat and water quality should be implemented according to the thresholds of these parameters.

Amphipods from marine cave sediments of the southern Iberian Peninsula: diversity and ecological distribution

Summary: The present study explores the amphipod assemblages of six marine caves on the Mediterranean coast of southern Spain. Replicate samples were taken both inside and outside each marine cave in order to characterize the amphipod fauna and the physicochemical properties of the sediment. As a result, 44 amphipods species were identified. The high number of species found in a relatively limited area highlighted the richness of the Alboran Sea fauna, which is mainly due to the mixture of species from different biogeographic areas. Harpinia genus was the dominant amphipod taxa inside marine caves and Perioculodes longimanus was also very abundant in the caverns. On the other hand, external communities were dominated by Siphonoecetes sabatieri, Metaphoxus fultoni and Photis longipes. There was a high degree of variability in both the internal and the external stations. Only the external station situated at low-medium depth showed a relatively homogeneous amphipod assemblage. The structure and behaviour of soft-bottom communities inside marine caves is difficult to predict because their environmental conditions depend on a particular combination of factors such as topography, depth and orientation. Therefore, no constant patterns were observed for species richness, Shannon diversity and abundance of amphipods in marine caves in comparison with open habitats. According to canonical correspondence analysis, sediment granulometry, organic matter and nitrogen concentration were the parameters that best explained the distribution of amphipods. Species were also classified by their tolerance to environmental pollution according to criteria followed by the Azti Marine Biotic Index and the BENTIX index. The great abundance of sensitive species at both the internal and external stations indicates the good ecological quality of the soft bottom studied. However, the suitability of biotic indices in marine caves should be tested in future studies.

Estimating Trends of Population Decline in Long-Lived Marine Species in the Mediterranean Sea Based on Fishers' Perceptions

We conducted interviews of a representative sample of 106 retired fishers in Italy, Spain and Greece, asking specific questions about the trends they perceived in dolphin and shark abundances between 1940 and 1999 (in three 20 year periods) compared to the present abundance. The large marine fauna studied were not target species of the commercial fleet segment interviewed (trawl fishery). The fishers were asked to rank the perceived abundance in each period into qualitative ordinal classes based on two indicators: frequency of sightings and frequency of catches (incidental or intentional) of each taxonomic group. The statistical analysis of the survey results showed that both incidental catches and the sighting frequency of dolphins have decreased significantly over the 60+ years of the study period (except for in Greece due to the recent population increase). This shows that fishers' perceptions are in agreement with the declining population trends detected by scientists. Shark catches were also perceived to have diminished since the early 1940s for all species. Other long-lived Mediterranean marine fauna (monk seals, whales) were at very low levels in the second half of the 20th century and no quantitative data could be obtained. Our study supports the results obtained in the Mediterranean and other seas that show the rapid disappearance (over a few decades) of marine fauna. We show that appropriately designed questionnaires help provide a picture of animal abundance in the past through the valuable perceptions of fishers. This information can be used to complement scientific sources or in some cases be taken as the only information source for establishing population trends in the abundance of sensitive species.

Combining time trends in multiple metrics for identifying persistent changes in population processes or environmental stressors

Summary1. Metrics have become a standard way for summarizing environmental monitoring results. Different metrics react differently to natural variations and human‐induced stressors. We suggest that combined analysis of time trends in selected biological metrics allows identification of biological processes (e.g. individual growth, mortality or recruitment) that have changed (increased or decreased) persistently. Alternatively, time trends in the abundance of sensitive species could indicate changes in environmental stressors.2. We calculate the joint likelihood of time trends in three metrics and use it to evaluate the evidence in the data for different combinations of metric time trends. A simulation study provides guidelines for interpreting log‐likelihood differences.3. We illustrate the approach for identifying biological process changes for three North Sea fish stocks (codGadus morhua, lesser‐spotted dogfishScyliorhinus caniculaand whitingMerlangius merlangius) using metrics derived from international bottom‐trawl survey data for the period 1997–2008. Over the period, a decrease in recruitment and several simultaneous process changes were most likely for cod, while a recruitment increase, mortality decrease and several process changes were most likely for lesser‐spotted dogfish. No significant persistent process changes were found for whiting.4. Synthesis and applications. The likelihood approach offers a way of combining monotonic time trends in multiple metrics for identifying persistent changes in exploited populations or environmental stressors, given suitable metric time series and tables for interpreting joint time trends. For data rich fish populations, the proposed method can supplement analytical stock assessments. For many other populations with no fisheries‐dependent data, it offers a way to identify population changes, which will be crucial for implementing the ecosystem approach to fisheries management and the European marine strategy framework directive.

Potential Approaches to Developing Lichen-Based Critical Loads and Levels for Nitrogen, Sulfur and Metal-Containing Atmospheric Pollutants in North America

“Critical load” and “critical level” (the deposition or concentration, respectively, of atmospheric pollutants above which negative ecosystem effects occur) concepts are reviewed for the North American lichenological community with the objective of stimulating interest and participation in this emerging field of research. We focus on how regional, lichen-based critical loads for nitrogen-, sulfur- and metal-containing pollutants could be developed for various terrestrial ecosystems in the U.S. utilizing existing data. Specifically we provide examples of how lichen community and element concentration responses to air pollution can be linked with measured or modeled estimates of depositional air pollutants. Preliminary critical loads of 0.26–0.33 kg ha−1 yr−1 for deposition of inorganic N in fine particulates and critical levels of 0.044–0.055 mg L−1 for wet deposition of ammonium ions are suggested for coniferous forests of western Oregon and Washington. These correspond to initial declines in presence and abundance of sensitive species and a % N concentration of 0.55–0.61 in Platismatia glauca. Indicator species distribution and abundance as well as physiological, morphological, growth or reproduction responses can also be used to set critical loads. Further research needs are identified.

Patterns of fish community composition along a river affected by agricultural and urban disturbance in south-central Chile

Patterns of fish community composition in a south-central Chile river were investigated along the altitudinal-spatial and environmental gradient and as a function of anthropogenic factors. The spatial pattern of fish communities in different biocoenotic zones of the Chillan River is influenced by both natural factors such a hydrologic features, habitat, and feeding types, and also by water quality variables which can reduce the diversity and abundance of sensitive species. A principal component analysis incorporating both water quality parameters and biomarker responses of representative fish species was used to evaluate the status of fish communities along the spatial gradient of the stream. The abundance and diversity of the fish community changed from a low in the upper reaches where the low pollution-tolerant species such as salmonid dominated, to a reduced diversity in the lower reaches of the river where tolerant browser species such as cypriniformes dominated. Even though the spatial pattern of fish community structure is similar to that found for the Chilean Rivers, the structure of these communities is highly influenced by human disturbance, particularly along the lower reaches of the river.

Effects of Metals on Stream Macroinvertebrate Assemblages from Different Altitudes

We tested the hypothesis that macroinvertebrate assemblages from streams of different size (third‐ and fourth‐order) and altitude (2545 and 2320 m above sea level) varied in their sensitivity to metals. We exposed macroinvertebrates collected from these sites to metals in streams microcosms and compared their responses to those measured at reference and metal‐polluted sites at different altitudes. Densities of macroinvertebrate assemblages from the small, high‐altitude stream were reduced more in metal‐dosed microcosms than those from the large, low‐altitude stream. Results from the field survey were similar to experimental results, as densities of organisms from metal‐polluted sites in small, high‐altitude streams were lower than those of the same taxa in larger, lower‐altitude streams. There are a number of factors that may contribute to the variation in metal sensitivity we observed, such as difference in abiotic factors or abundance of sensitive species between high‐ and low‐altitude streams. In addition, differences in insect body size or phenology may have contributed to some of the observed variation in response. Since invertebrate assemblages from high‐altitude sites were 12‐84% more sensitive to metals, we suggest that metal criteria incorporate factors to allow for such differences to protect aquatic life.