Nitrate reductase activity in macroalgae and its vertical distribution in macroalgal epiphytes of seagrasses.

Macroalgal epiphytes within seagrass meadows make a significant contribution to total primary production by assimilating water column N and transferring organic N to sediments. Assimilation of NO3 – requires nitrate reductase (NR, EC 1.6.6.1); NR activity represents the capacity for NO3 – assimilation. An optimised in vitro assay for determining NR activity in algal extracts was applied to a wide range of macroalgae and detected NR activity in all 22 species tested with activity 2 to 290 nmolNO3 – min–1 g–1 frozen thallus. With liquid-N2 freezing immediately after sample collection, this method was practical for estimating NR activity in field samples. Vertical distribution of NR activity in macroalgal epiphytes was compared in contrasting Posidonia sinuosa and Amphibolis antarctica seagrass meadows. Epiphytes on P. sinuosa had higher mass-specific NR activity than those on A. antarctica. In P. sinuosa canopies, NR activity increased with distance from the sediment surface and was negatively correlated with [NH4 +] in the water but uncorrelated with [NO3 –]. This supported the hypothesis that NH4 + released from the sediment suppresses NR in epiphytic algae. In contrast, the vertical variation in NR activity in macroalgae on A. antarctica was not statistically significant although there was a weak correlation with [NO3 –], which increased with distance from the sediment. Estimated capacities for NO3 – assimilation in macroalgae epiphytic on seagrasses during summer (24 and 46 mmolN m–2 d–1 for P. sinuosa and A. antarctica, respectively) were more than twice the estimated N assimilation rates in similar seagrasses. When the estimates were based on annual average epiphyte loads for seagrass meadows in other locations, they were comparable to those of seagrasses. We conclude that epiphytic algae represent a potentially important sink for water-column nitrate within seagrass meadows.

Non-indigenous marine macroalgae in native communities: a case study in the British Isles

It has traditionally been considered that areas with high natural species richness are likely to be more resistant to non-indigenous species than those with lower numbers of species. However, this theory has been the subject of a debate over the last decade, since some studies have shown the opposite trend. In the present study, a macroalgal survey was carried out at 24 localities in Northern Ireland and southern England, using a quadrat approach in the lower littoral. The two opposing hypotheses were tested (negative versus positive relationship between native and non-indigenous species richness) in this marine environment. The effect of the presence of 'impacts', potential sources of disturbance and species introduction (e.g. marina, harbour or aquaculture), was also tested. A positive relationship was found between the number of non-indigenous species and the native species richness at the three different scales tested (quadrats, sites and localities). At no scale did a richer native assemblage appear to restrict the establishment of introduced species. The analyses revealed greater species richness and different community composition, as well as more non-indigenous species, in southern England relative to Northern Ireland. The presence of the considered impacts had an effect on the community composition and species richness in southern England but not in Northern Ireland. Such impacts had no effect on the non-indigenous species richness in either area.

Textile wastewater treatment using granular activated carbon adsorption in fixed beds

This work involved the treatment of industrial wastewater from a nylon carpet printing plant which currently receives no treatment and is discharged to sea. As nylon is particularly difficult to dye, acid dyes are required for successful coloration and cause major problems with the plant's effluent disposal in terms of color removal. Granular activated carbon Filtrasorb 400 was used to treat a ternary solution of acid dyes and the process plant effluent containing the dyes in a fixed-bed column system. Experimental data were correlated using the bed depth service time (BDST) model to previously published work by the authors for single dye adsorption. The results were expressed in terms of the BDST adsorption capacity, in milligrams of adsorbate per gram of adsorbent, and indicated that there was a 12-25% decrease iri adsorption capacity in the ternary system compared to the single component system; This reduction has been attributed to competitive adsorption occurring in the ternary component system. Dye adsorption from the process plant effluent showed an approximate 65% decrease in adsorption capacity compared to the ternary solution system. This has been attributed to interference caused by the other colorless textile effluent pollutants found in the process wastewater. A chemical oxygen demand analysis on these components indicated that the dyes accounted for only 14% of the total oxygen demand.

Do mussel patches provide a refuge for algae from grazing gastropods?

On rocky shores, cover of macroalgae is often greater growing epibiotically on mussels compared to algae growing directly attached to rock. A survey of two shores on the east coast of Ireland confirmed that mussel beds contained greater percentage algal cover and more diverse algal assemblages compared to those on rock. The reasons for this difference are not clear. It has been suggested that mussel beds provide a refuge for algae from grazing gastropods. Surprisingly, we found no evidence to support this. Using wax discs, gastropod grazing patterns were found to be similar within the mussel beds as on rock. The mussel beds do not appear to provide a refuge for algae from grazing activity at this scale and we suggest other possible mechanisms for the prevalence of epibiotic algal cover on mussels. Intertidal grazers may in fact affect the epibiotic algae on mussels and thereby affect indirectly the persistence of mussel beds.

The last meal of the Late Ordovician mollusc ‘Helminthochiton’ thraivensis Reed, 1911, from the Lady Burn Starfish Beds, southwest Scotland.

An exceptional specimen of the Late Ordovician mollusc ‘Helminthochiton’ thraivensis Reed, from the Katian of the Lady Burn Starfish Beds, southwest Scotland, preserves gut contents that include nine pelmatozoan ossicles. These are interpreted as including two nodal and five intermodal columnals, and two radice ossicles from the attachment structure. The stem was cyclocyclic and heteromorphic, possibly N212. Radice ossicles were wider than the height of nodals, so radice scars must have encroached onto the latera of adjacent pluricolumnals. These features were compared with the 26 known pelmatozoan taxa from the Lady Burn Starfish Beds. Paracrinoids (one species) and glyptocystitid rhombiferans (six species) were discounted as prey because of their cemented attachment, and incorrect columnal morphology and lack of attachment, respectively. Of 19 species of crinoids, eight are discounted in which the column is pentagonal, tetragonal or unknown. Of the remaining eleven species, only the monobathrid camerate Macrostylocrinus cirrifer Ramsbottom satisfies all criteria for identification of the prey, including heteromorphy and radice scars encroaching adjacent internodals.