Elsevier

Ecological Indicators

Volume 29, June 2013, Pages 167-178
Ecological Indicators

Development of a macroinvertebrate multimetric index for the assessment of low-land streams in the neotropics

https://doi.org/10.1016/j.ecolind.2012.12.030Get rights and content

Abstract

The water and habitat quality in Panamanian streams and rivers are being degraded by agriculture, urbanization, industrial activities, mining, and other forms of development. Thus, the need for standards, especially those examining the biological attributes of lotic systems, are urgently required. We describe the development of a multimetric index based on macroinvertebrates collected in low-land streams in the Panama Canal Watershed (PCW), which differed in their levels of human impacts. The index was developed using 12 streams and validated using a further three, all of which were sampled on four occasions, in the dry and wet seasons of 2007 and 2008. We examined 42 metrics related to macroinvertebrate community structure, composition, and function. Based on their ability to distinguish reference from moderately or severely impacted streams, and on their independence, we selected seven metrics (Margalef's index (taxa), Shannon's evenness index (taxa), number of EPT (taxa), % of Trichoptera, ratio of Chironomidae/Diptera individuals, % of scrapers, and % of shredders). These metrics were then standardized and developed into the Neotropical Low-land Stream Multimetric Index (NLSMI). Overall, the NLSMI distinguished well among the different levels of impairment (Reference, Moderate impact, and Severe impact) and showed a strong, significant correlation with principal component analysis (PCA) axis one values, with the PCA based on a set of physico-chemical variables indicative of stream quality. The wet season generally resulted in lower NLSMI values, leading us to suggest that sampling for biomonitoring be carried out in the dry season. Overall, this preliminary macroinvertebrate NLSMI shows promise for developing a biomonitoring programme to assess the ecological integrity of streams, to aid with management, restoration, and conservation, and to serve as a basis to develop a more geographically extensive multimetric index.

Highlights

► We examined macroinvertebrate community structure, composition, and function metrics. ► Seven metrics were selected that distinguished reference from human-impacted streams. ► We developed the Neotropical Low-land Stream Multimetric Index (NLSMI). ► Seasonal variation in NLSMI values was observed – dry season best for sampling. ► Macroinvertebrate NLSMI shows promise for developing a biomonitoring programme.

Introduction

Water is often regarded as the most essential of natural resources, with streams and rivers being the primary source of renewable water for both humans and freshwater ecosystems (Karr and Chu, 2000, Vorosmarty et al., 2010), as well as providing habitat for a great diversity of organisms (Dudgeon et al., 2006). Yet lotic ecosystems are among the most threatened by human activities, with only a very small fraction still unaffected by humans (Dudgeon et al., 2006, Strayer and Dudgeon, 2010, Vorosmarty et al., 2010). The World Wildlife Foundation (2012) Living Planet Report described the Living Planet Index (LPI), which reflects the health of the planet's ecosystems by examining the population trends of 2500 vertebrate species. They reported that tropical freshwater biodiversity was most imperilled, with the LPI declining on average 70% from 1970 to 2008. Land-cover change through agricultural development, urbanization, industrialization, mining, reservoir development, and irrigation result in pollution (e.g., excessive sediment, organic, metal) (de Jesus-Crespo and Ramirez, 2011, Yule et al., 2010), as well as habitat and hydrological changes (Power et al., 1996), which can severely affect the ecological health of lotic environments and their biota (Vorosmarty et al., 2010). Furthermore, efficient management practices, restoration efforts, and conservation of stream and river systems can be hampered by a lack of clear standards to judge the degree and trend of environmental degradation (Moya et al., 2007, Weigel et al., 2002).

The best method to understand and help control human impacts on lotic systems comes from information on the condition (health) of their aquatic biotas, which respond to changes in water quality, habitat structure, flow regime, energy sources, and biotic interactions (Karr, 1981, Karr, 1999, Karr and Chu, 2000). Biota respond to all types of environmental stressors, as well as combinations and synergisms of stressors, an advantage over traditional physical and chemical measures. Benthic macroinvertebrates are the group of organisms most widely used for water-quality assessment because of their suitable life-history characteristics and diversity (Bonada et al., 2006, Resh et al., 1995). Several multimetric indices based on benthic macroinvertebrates have been successfully developed in the neotropics including: Weigel et al. (2002) in west-central Mexico; Silveira et al. (2005) in south-east Brazil; Baptista et al. (2007) in the Atlantic forest of Brazil; Moya et al. (2007) in the Upper Isiboro-Sécure Basin and Moya et al. (2011) in three basins of the Bolivian Amazon; Oliveira et al. (2011) in the area of the Guapiaçu and Macau Rivers of Brazil; and Couceiro et al. (2012) in the Central Amazon region of Brazil. However, uncertainties still remain regarding the effects of sampling during the “wet” and “dry” seasons in the neotropics and the utility of certain EPT (Ephemeroptera, Plecoptera, and Trichoptera) groups. Moreover, there is a general lack of multimetric indices focusing on tropical low-land areas, which often experience the highest levels of human pressure, as well as the development of indices in Central America.

Indices of Biotic Integrity (IBI) use biota to evaluate the integrity of aquatic ecosystems and monitor responses and trends in the condition of communities that are associated with human impacts (Karr, 1981, Karr, 1999, Resh et al., 1995). The streams and rivers in the Panama Canal Watershed (PCW) are important for providing drinking water to the surrounding area, as well as for maintaining necessary water levels for shipping in the Panama Canal, especially during the four-month dry season. Moreover, as in many tropical regions, research on Panama's freshwater biota is still in its infancy (Dudgeon et al., 2006) and because of Panama's unique geologic history, diversity is likely very high (Kimsey, 1992). We sampled macroinvertebrates over two years from 15 streams, varying in human impacts levels, in the PCW. Using 12 of these streams we sought to determine which structural, compositional, and functional measures provided the best separation of non-impacted and impacted stream sites and further developed this into a preliminary multimetric index. We confirmed the applicability of the multimetric index using the three remaining streams, and by comparing index values to principal component analysis (PCA) axis-one values based on physico-chemical variables indicative of stream quality. In addition, we examined the influence of season on the multimetric index. Providing a preliminary multimetric index will aid management decisions pertaining to the conservation of freshwater biodiversity in this region, and represent a starting point for the further development of biotic indices in Panama and the neotropics.

Section snippets

Study area

The PCW, in the Republic of Panama (Fig. 1), occupies an area of 2892 km2, with the majority of its landmass occurring at elevations below 300 m. The region is moist tropical (latitude 9°N), with temperatures remaining stable throughout the year (average 23–27 °C). The average precipitation in the PCW is 2921 mm yr−1, with all of our sampling areas receiving between 2000 and 3000 mm yr−1. The bulk of precipitation occurs during the wet season, from May to December, with much smaller amounts (about

Environmental variables

Watershed characteristic variables (e.g., slope, site elevation) did not differ significantly between reference sites and sites having various levels of impairment (Table 2). In contrast, the predominant land-use types differed significantly among the reference and impaired sites, with reference sites having significantly higher percentages of primary forest and lower percentages of populated areas, shrubland, Saccharum spontaneum, pastures, and bare ground (Table 2). Reference stream

Discussion

One important consideration when developing a multimetric index is its ability to distinguish between natural variability and human alterations (Karr and Chu, 1999, Moya et al., 2007). Therefore, both the reference and impacted sites that are chosen should be as similar as possible, so that the effects of human impacts can be assessed properly (Hawkins et al., 2010). Factors such as elevation, stream size (order), and surface geology have been found to affect factors such as taxon and EPT

Conclusions

Our benthic macroinvertebrate NLSMI was able to distinguish between reference and moderately impacted and severely impacted sites, providing a good indication of the ecological status of these streams. NLSMI values were generally lower in the wet-season, likely because of natural changes in the community; therefore, we recommend bioassessment sampling in the dry-season. We also recommend testing the index on a larger geographical area to explore its universality. The broad perspective offered

Acknowledgments

We thank the Autoridad Nacional del Ambiente (ANAM) for collection permits SE/A-75-06 and SE/A-4-08, and for the export permits SEX/A-110-07 and SEX/PH-1-08. Vouchers have been placed in the herbarium at the University of Panama and Museo de Invertebrados Fairchild. We are grateful to the Instituto de Investigaciones Científicas y Servicios de Alta Tecnología (INDICSAT) for the use of their facilities to perform water chemistry analyses, the Autoridad del Canal de Panamá (ACP) for access to

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