Faunal Colonization of Submarine Mine Tailings: An Intertidal Experiment to Investigate the Infuence of Sediment Organic Carbon Content

Abstract

Current financial estimates of mineral mining in Norway are approximately 12 billion NOK per year. Most of the industry is located close to the coastline and the inert waste produced ( tailings', granulometrically similar to sand) is currently deposited in adjacent fjords as Submarine Tailings Placements (STPs). Deposition of STPs smothers the local resident biological assemblages and observations at current sites indicate that colonization, and therefore ecosystem recovery, is slow. This is hypothesized to result from the lack of organic carbon within such deposits. To test this hypothesis, and to determine the optimum concentration of organic carbon to enhance the colonization process, I conducted an intertidal experiment in the Crouch Estuary, Essex (UK) from April 2012 to April 2013. The experiment comprised tailings treatments ranging in organic carbon concentrations from 0 to 5%. Samples for fauna, sediment grain size, and carbon and nitrogen content were collected and redox potentials measured at T = 0, 45, 115, 180 and 365 days. Univariate indices and community structure was investigated by looking at different aspects of the collected benthic macrofauna. The data revealed that a concentration of 0.5% organic carbon was the optimum concentration to enhance macrofaunal colonization in this study, and after one year the majority of the univariate indices indicated recovery in the mine tailings with a low concentration of organic carbon. However, the macrofaunal communities functioned differently and had a far less total production than the ambient sediments. This indicates that factors other than organic carbon are important when it comes to colonization of mine tailings, and these factors are discussed. The use of diversity indices in comparison to other more elaborate methods to determine the ecological state of the benthic community is also discussed.