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 (EhNHE) 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 EhNHE 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 EhNHE and GS at lease and non-lease locations had similar slopes but intercept values were significantly higher for S and lower for EhNHE (p <0.007) for lease locations. EhNHE and a Benthic Enrichment Index derived from EhNHE, 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 EhNHE.