Influence of mussel aquaculture on sediment organic enrichment in a nutrient-rich coastal embayment

Effects of mussel Mytilus edulis aquaculture on benthic organic enrichment were determined in Tracadie Bay, a shallow, nutrient-rich embayment in Prince Edward Island, Canada.Water content (WC), inorganic grain size (GS), organic matter (OM), redox potentials (Eh NHE ) and free sulfides (S) in the upper 2 cm of sediment were measured at 58 stations throughout the inlet to evaluate spatial variations between lease and non-lease locations.MANOVA results showed that mean (± SD) values for WC (64.8 ± 12.7%), OM (9.8 ± 4.3%), and S (1794 ± 771 µM) were significantly (p < 0.005) higher and Eh NHE lower (-51 ± 78 mV) within mussel leases (n = 24) vs. non-lease areas (n = 34).Negative regressions between S and GS and positive regressions between Eh NHE and GS at lease and non-lease locations had similar slopes but intercept values were significantly higher for S and lower for Eh NHE (p < 0.007) for lease locations.Eh NHE and a Benthic Enrichment Index derived from Eh NHE , OM and WC were inversely related to S. K-means clustering and multi-dimensional scaling showed that geochemical variables could be used to group stations into categories of benthic organic enrichment within mussel lease and non-lease areas characteristic of oxic-hypoxic sediments described by measures of S and Eh NHE .