The effects of petroleum exploitation on water quality bio-assessment and benthic macro-invertebrate communities in the Yellow River Delta wetland, Dongying

The major environmental risks associated with petroleum extraction (e. g. oil spills and leaks) are well known. There is a lot of information on the impacts of petroleum exploration on benthic communities in foreign studies. In this study, we probed the effects of petroleum exploration on macro-invertebrate assemblages, which are important components of benthic communities in this wetland ecosystem. The object of the investigation was to provide scientific data to guide the management, ecological restoration, conservation of biodiversity, and sustainable development of aquatic ecosystems. Physicochemical variables were measured at 34 sites in the Yellow River Delta wetland, Dongying, China, in October 2009, and benthic macro-invertebrate assemblages were collected using a D-frame net and a Peterson grab. The water body in the study area was oligohaline, its salinity ranging between 0.05 and 5 ppt. A total of 84 macro-invertebrate taxa, belonging to 70 genera, 41 families, 12 orders, 6 classes, and 3 phyla, were collected. Insecta comprised 52.4% of all benthic invertebrate taxa, of which Odonata and Diptera accounted for 23% and 24%, respectively. The structure and diversity of macro-invertebrate assemblages were expressed using the Shannon-Wiener index, the Margalef index and the dominance index. Water quality was assessed by the Shannon-Wiener index and the biotic index. The dominant species at most of the sites were either Chironomus spp. or Glyptotendipes spp. with overall dominance indices of 0.0315 and 0.0522, respectively. Pearson correlation analysis showed that the Shannon-Wiener index was negatively correlated with total nitrogen (TN) (r = -0.446, P = 0.02) but was not correlated with any of the other physicochemical variables measured. The biotic index was not correlated with any of the physicochemical variables. The numbers of molluscan taxa were negatively correlated with salinity (r = -0.422, P = 0.028) and positively correlated with pH (r = 0.435, P = 0.023). Likewise, the percentages of individual Mollusca at the sites were negatively correlated with salinity (r = -0.395, P = 0.041) and positively correlated with pH (r = 0.565, P = 0.002). The numbers of oligochaete taxa were significantly positively correlated with TN (r = 0.524, P = 0.005). The petroleum content of the water was not correlated with any of the biological indices and was not considered to be a major stressor. Canonical correspondence ordination analysis (CCA) showed that TN