Using multiple indicators to evaluate the ecological integrity of a coastal plain stream system

We demonstrate the use of multiple indicators to characterize the ecological integrity of a coastal plain stream system in the New Jersey Pinelands in relation to human-induced watershed alterations. The individual indicators include pH, specific conductance, stream vegetation and stream-fish, impoundment-fish, and anuran assemblages. We evaluate and compare the utility of the individual and multiple environmental and biological indicators and present a relatively straightforward method for ranking sites. Specific conductance and pH measured at 88 monitoring sites varied in relation to the percentage of altered land (developed land and upland agriculture) within the associated watersheds. All three environmental variables were associated with variations in the composition of stream vegetation and stream fish, impoundment fish, and anuran assemblages. With the exception of impoundment fish, the association between altered land and the multiple-indicator scores based on the two water-quality indicators and the four biological indicators was stronger than that displayed by any of the individual variables.     

Improving biological indicators to better assess the condition of streams

Biological indicators of stream condition are in use by water resource managers worldwide. The State of Maryland and many other organizations that use Indices of Biotic Integrity (IBIs) must determine when and how to refine their IBIs so that better stream condition information is provided. With completion of the second statewide round in 2004, the Maryland Biological Stream Survey (MBSS) had collected data from 2500 stream sites, more than doubling the number of sites that were available for the original IBI development. This larger dataset provided an opportunity for the MBSS to address the following shortcomings in the original IBIs: (1) substantial disturbance apparent in some reference sites, (2) fish IBIs could not be applied to very small streams, (3) natural variability within IBIs (based on regions) resulted in some stream types (e.g., coldwater and blackwater streams) receiving lower IBI scores and (4) one IBI was not able to discriminate degradation as desired (i.e., Coastal Plain fish IBI). Therefore, development of new fish and benthic macroinvertebrate IBIs was undertaken to achieve the goals of: (1) increased confidence that the reference conditions are minimally disturbed, (2) including more natural variation (such as stream size) across the geographic regions and stream types of Maryland and (3) increased sensitivity of IBIs by using more classes (strata) and different metric combinations. New fish IBIs were developed for four geographical and stream type strata: Coastal Plain, Eastern Piedmont, warmwater Highlands and coldwater Highlands streams; new benthic macroinvertebrate IBIs were developed for three geographical strata: Coastal Plain, Eastern Piedmont and Highlands streams. The addition of one new fish IBI and one new benthic macroinvertebrate IBI partitioned natural variability into more homogeneous strata. At the same time, smaller streams (i.e., those draining catchments <300 ac), which constituted a greater proportion of streams (25%) sampled in Round Two (2000–2004) than Round One (1995–1997), because of the finer map scale, were included in the reference conditions used to develop the new IBIs. The resulting new IBIs have high classification efficiencies of 83–96% and are well balanced between Type I and Type II errors. By scoring coldwater streams, smaller streams and to some extent blackwater streams higher, the new IBIs improve on the original IBIs. Overall, the new IBIs provide better assessments of stream condition to support sound management decisions, without requiring substantial changes by cooperating stream assessment programs.     

Exploring the dynamics of ecological indicators using food web models fitted to time series of abundance and catch data

Previously, standardized snap-shot models of the Southern Benguela (1980–1989), Southern Humboldt (1992) and Southern Catalan Sea (1994) ecosystems were examined and found to facilitate assessment of ecosystem characteristics related to the gradient in exploitation status of the ecosystems; highest level of exploitation in the South Catalan Sea (North-western Mediterranean), high in the Southern Humboldt and lower in the Southern Benguela. Subsequently, these models were calibrated and fitted using available catch, fishing effort/mortality and abundance data series and incorporated environmental and internal drivers. This study furthers the previous comparative analyses by comparing changes in ecosystem structure using a selection of ecosystem indicators from the calibrated models and assessing how these indicators change over time in these three contrasting ecosystems. Indicators examined include community turnover rates (production/biomass), trophic level of landings and the community, biodiversity indicators, ratios of predatory/forage fish and pelagic/demersal fish biomass, catch ratios, and network analysis indicators. Using the set of model-derived indicators, the three ecosystems were ranked in terms of exploitation level. This ranking was performed using the values of these indicators in recent years (ecosystem state) as well as their trends over time (ecosystem trend). The non-parametric Kruskal–Wallis and Median tests were used to test for significance of the difference between indicators from the three ecosystems in the last 5 years of the simulation to compare present ecosystem states. We compared the slope of the lineal trend and its significance between ecosystems using the generalized least-squares regression taking auto-correlation into consideration to analyse ecosystem trends. The indicators that capture better the high impacts of fishing prevalent in the Mediterranean and Humboldt ecosystems, and the more conservative exploitation of the Southern Benguela, are the fish/invertebrates biomass and catch ratio, the demersal/pelagic fish biomass and catch ratio (depending on the ecosystem and the fishery being developed), flows to detritus, and the mean trophic level of the community (when large, poorly quantified groups such as zooplankton and detritus are excluded). This study suggests that the best option for classifying ecosystems according to the impact of fishing is to consider a broad range of indicators to understand how and why an ecosystem is responding to particular environmental or fishing drivers (or more likely a combination of these). Our results highlight the importance of including indicators capturing trends over time as well as recent ecosystem states. We also identified 23 pairs of indicators that correlated similarly in the three ecosystems (they showed a significant correlation with same sign). Further comparisons may contribute towards generalization of this list, progressing towards a better understanding of the behaviour of ecological indicators.     

Use of atrazine sensitive leguminous plants as biological indicators to evaluate the atrazine degradation efficiency of a bacterial inoculum

Atrazine sensitive leguminous plants were grown in a soil spiked with atrazine and augmented with an atrazine-degrading bacterium, Arthrobacter sp. strain MCM B-436, to ascertain its degradative efficiency. Germination and survival of plants was correlated with atrazine removal from soil. This experiment was carried out at laboratory as well as field level, showing consistent results. This bioindicator approach serves as an efficient measure for atrazine removal and could be easily adapted to determine atrazine degradation efficiency of other microbial strains.