The diet and influence of the spionid polychaete Marenzelleria on benthic communities in coastal Newfoundland

Spionid polychaetes within the genus Marenzelleria are common inhabitants of organically enriched sediments in the Northern hemisphere. The species M. viridis has unique ventilation behaviors that create dynamic, fluctuating oxygen conditions in sediments, enhancing sulfate reduction. These behaviours may have negative effects on other macrofauna and positive effects on sulfur bacteria. A Marenzelleria species recently sampled in Newfoundland is here identified as M. viridis, and its abundance correlates little with abiotic factors and macrofaunal community composition at examined sites. Various types of surrounding sediments (oxic and suboxic as well as M. viridis burrow linings) contained surprisingly similar total prokaryotic, sulfate reducing and sulfur oxidizing bacteria numbers. The high abundance of sedimentary prokaryotes, combined with the stable isotopic composition of M. viridis tissues and lack of obvious symbionts, suggest that, thanks to its ventilation behaviour, this species may “farm” sulfur bacteria in sediments and use them as a primary food source.

Fresh biomass of macroalgae collected at Hansneset, Kongsfjorden, Spitsbergen in 1996/1998

We surveyed macroalgae at Hansneset, Blomstrand in Kongsfjorden, Svalbard, down to 30 m depth between 1996 and 1998. In total, 62 species were identified: 16 Chlorophyta, 25 Phaeophyceae, and 21 Rhodophyta. The majority of species (53.5%) belonged to the Arctic cold-temperate group, followed in frequency by species distributed from the Arctic to the warm-temperate region (25.9%). Four endemic Arctic species (Laminaria solidungula, Acrosiphonia flagellata, A. incurva, and Urospora elongata) were found. Two species (Pogotrichum filiforme and Mikrosyphar polysiphoniae) were new to Svalbard. Chlorophyta, Phaeophyceae, and Rhodophyta extended from the eulittoral zone down to 11, 21, and >30 m depths with maximum biomasses at 1-5 m, 5-10 m, and 5-30 m depths, respectively. Annual and pseudoperennial species had highest biomasses in the upper 5 m, while perennials were distributed deeper. The highest biomass (8600 g/m**2 wet weight) at 5 m depth comprised mainly L. digitata, Saccorhiza dermatodea, Alaria esculenta, and Saccharina latissima. The biogeographic composition of macroalgae at Hansneset was rather similar to that of northeastern Greenland, but different from that of northern Norway, which has a higher proportion of temperate species. Climate warming and ship traffic may extend some of the distribution ranges of macroalgae from mainland Norway to Svalbard.