Abstract
Previous studies have shown clearly that the deposit feeding polychaete, Hediste diversicolor, can promote oxygenation of sediments exposed to excess loads of mussel faeces. In this experimental study, we explicitly test their utility as food for H. diversicolor to survive and grow on. Furthermore, in order to understand the consequences of experimental manipulations, we also evaluated effects on chemical fluxes in and out of the sediment. The results show strong differences in growth but no difference in short-term survival. Fed only on mussel faeces, the polychaetes grew on average 17% in wet weight after a period of 10 days, compared to 3% when given equivalent amounts of organic matter from the natural sediments. Addition of faeces to natural sediments resulted in 19–20% growth, thus suggesting an approximate additive effect of the two food sources. Chemical analyses showed that, oxygen consumption increased with load of organic material irrespective of origin, faecal material caused higher fluxes of ammonia compared to natural organic material, but neither oxygen consumption nor nutrient fluxes were affected by the ashing of sediments. In contrast, fluxes of silicate increased as a consequence of ashing but were not affected by the addition of mussel faeces. Thus, despite risks of experimental artefacts due to ashing of sediments, the results show that oxygen and nutrient dynamics responded to manipulations of organic material and not to the potential modification of sediment structure. Therefore, the observed effects on growth of H. diversicolor can be safely interpreted as caused by differences in amount and quality of organic material. Mussel faeces is a high-quality food source for this species of polychaete and, in combination with ample evidence from previous studies that bioturbation, we conclude that H. diversicolor is a suitable candidate in further efforts to develop technical solutions based on bioturbation for mitigation of adverse effects on benthic environments in connection with mussel-farming.
Highlights
In estuaries and coastal areas, organic matter in sediments is generally a mixture of residues from micro- and macroalgae, plankton and plant material from land (Hu et al 2009)
The sieved sediment was mixed to achieve a homogenous sediment blend and divided into three parts for different treatments: (1) sediment was kept untreated as a natural organic matter sediment, (2) mussel faeces was added to the natural sediment yielding the double amount of organic matter compared to the N treatment (NF) and (3) sediment was treated to remove the organic matter by ashing in 520 °C for 12 h before mussel faeces were added to the same level of organic content as the N treatment creating a Bfaeces sediment^ (F)
By manipulating levels of naturally occurring organic matter and of faecal material from mussels, we have shown that the burrowing polychaete Hediste diversicolor can use organic material deposited in mussel faeces as a high-quality food source
Summary
In estuaries and coastal areas, organic matter in sediments is generally a mixture of residues from micro- and macroalgae, plankton and plant material from land (Hu et al 2009). Organic input to that lead to a series of changes to the chemical and physical properties of the sediment (Schaanning 1994). Organic enrichment of the sediment can result in benthic responses such as increased bacterial abundance, changes (e.g. in abundance, composition) in meiofaunal community and reduced abundance and diversity of benthic macrofauna (Pearson and Rosenberg 1978; Chamberlain et al 2001). The extent of the environmental impact depends on the local assimilative capacity and the input amount of organic matter (Black 2001). The severity of the organic enrichment of farms is highly sitespecific and is influenced by several environmental factors, such as the hydrodynamics at the farm site (Chamberlain et al 2001; Hartstein and Rowden 2004)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
