ALBERT

Description: A new species of terebellid polychaete, Lanice arakani sp. nov., is described from two specimens collected in deep water at seamounts of the west Pacific by the submersible `JAGO', and comparisons are made with the established species of the genus. Special reference is given to the morphology of the worm's sediment tube and in situ observations.

Description: A study on cod egg mortality was carried out in the Bornholm Basin (southern central Baltic Sea) toward the end of July 1996. An initial egg aggregation marked by a satellite-tracked drifter buoy was sampled repeatedly over an 11-day period; profiles of temperature, salinity and dissolved oxygen were concurrently recorded. Three replicate estimates of mortality were obtained for each pair of subsequent developmental stages from newly spawned eggs to early larvae. A consistent pattern of stage-specific mortality coincided well with previous experimental observations. Average daily mortality rates were 7.2% (eggs IA/IB), 38.7% (eggs (IB/II), 25.6% (eggs II/III), 40.0% (eggs III/IV), and 42.3% (eggs IV/early larvae). The cumulative mortality until hatch amounted to 99.9%. Results from hydrodynamic modelling, however, indicated that the drifter's trajectory was influenced by wind stress. Hence, the mortality rates might be biased despite the short sampling intervals; a modification of the sampling design is recommended for future studies.

Description: Recent seismic field work has revealed high lower-crustal velocities under Ninetyeast Ridge, Indian Ocean, indicating the presence of crustal underplating (Grevemeyer et al. 2000). We used results from Ocean Drilling Program (ODP) drill cores and cross-spectral analysis of gravity and bathymetric data to study the impact of the underplating body on the subsidence history and the mode of isostatic compensation along Ninetyeast Ridge. Compared with the adjacent Indian basin, the subsidence of Ninetyeast Ridge is profoundly anomalous. Within the first few millions of years after crustal emplacement the ridge subsided rapidly. Thereafter, however, subsidence slowed down significantly. The most reliable model of isostasy suggests loading of a thin elastic plate on and beneath the seafloor. Isostatic compensation of subsurface loading occurs at a depth of about 25km, which is in reasonably good agreement with seismic constraints. Subsurface loading is inherently associated with buoyant forces acting on the lithosphere. The low subsidence may therefore be the superposition of cooling of the lithosphere and uplift due to buoyant material added at the base of the crust. A model including prolonged crustal growth in the form of subcrustal plutonism may account for all observations.

Description: Available data support a mechanism of buoyancy‐mediated vertical migration by large‐sized diatoms of Rhizosolenia spp. as a means to access “new” nitrogen from deep waters. To assess whether phytoplankton simultaneously satisfy their Fe requirements by this mechanism, field samples collected during summer 1996 at stations located along a transect through the central North Pacific gyre were assayed for the presence of flavodoxin and ferredoxin via Western blot analysis. All samples, regardless of their buoyancy status and the station from which they were collected, had accumulated flavodoxin but not ferredoxin. To understand better the significance of the field results, cultures of Rhizosolenia formosa H. Peragallo were grown in the laboratory with varying levels of total Fe (200 nM–10,000 nM). Fe had little effect on the physiological and photochemical parameters measured for each treatment. Growth rates did not exceed 0.17 d−1 and values of Fv/Fm ranged from 0.48 to 0.62. In addition, R. formosa accumulated only flavodoxin at each level of Fe addition. From these results, it appears that for some rhizosolenids, flavodoxin is constitutively expressed. The underlying basis for the constitutive nature of this flavodoxin is unclear at present, although it is likely that it is ultimately related to chronic Fe deficit incurred in natural waters.

Description: Aquaculture in Germany is a small industry, practiced only in a few specifically suited areas. Marine finfish farming is almost nonexistent but mussel farming is a steady activity with a notable level of production. However, this industry is presently very restricted with no hope for expansion as regulations are stringent and new licences in both fresh and marine waters are extremely difficult to obtain. In addition to State-specific conditions within the Federation, the complexity of the regulatory framework is exemplified by focusing on some key aspects for finfish farming and by specific aspects of mussel farming activities in the Schleswig-Holstein Wadden Sea where environmental protection measures dictate the level of control, mainly as a result of the recent establishment of the National Wadden Sea Park.

Description: Empirical relationships are presented to estimate in fishes, asymptotic length (L∞) from maximum observed length (Lmax), length at first maturity (Lm) from L∞, life span (tmax) from age at first maturity (tm), and length at maximum possible yield per recruit (Lopt) from L∞ and from Lm, respectively. The age at Lopt is found to be a good indicator of generation time in fishes. A spreadsheet containing the various equations can be downloaded from the Internet at http://www.fishbase.org/download as popdynJFB.zip. A simple method is presented for evaluation of length–frequency data in their relationship to L∞, Lm and Lopt. This can be used to evaluate the quality of the length–frequency sample and the status of the population. Three examples demonstrate the usefulness of this method. 2000 The Fisheries Society of the British Isles

Description: A major vector for unintentional species introductions is international shipping. A wide range of organisms have been transported over long distances in ships' ballast tanks and as hull fouling. Although many desk studies and ship sampling programmes have been carried out, little information is available on changing numbers of individuals in ballast water during voyages. Detailed information could assist in evaluating the dimension of species import and future risks of unintentional species introductions by ballast water. The first European study, organised as a concerted action team and financed by the European Union, carried out several long-term and short-term workshops on board ships undertaking international voyages. The preliminary results from sampling the ballast water of the first four oceangoing workshops of this Concerted Action showed a decrease in numbers of specimens and taxa over time.

Description: Water and sediment quality conditions in and around a cage culture unit located in Wismar Bay (Western Baltic Sea, Germany) were investigated during summer 1994 using bacterial group indicators (Enterobacteriaceae, saprophytic bacteria and Vibrio, determined on selective media). Fish were fed once daily with extruded commercial pellets. Over a period of 8 days samples were taken before and after feeding at different sampling points close to or at the cages. The results showed that a drastic (up to 10 times) increase in different bacterial groups occurred inside the cages 10 min after feeding as well as occasionally in the surrounding water. Additional electron-microscopic observations of the bacterial biofilm on the cage nets revealed that a decrease (in comparison with the original number) in total bacteria on the net materials of 9.5 up to 42.8% occurred after feeding. It was concluded that water mixing caused by frenzied swimming just before and during feeding caused a release of bacteria which were growing vigorously on the surfaces of the cage system. Since the pathogenity and hydrophobicity of bacteria are closely related, this process of redistribution of bacteria into the water column could constitute an important stress factor for fish, which could probably also have a negative effect on fish production.

Description: Macroalgal blooms are a growing environmental problem in eutrophic coastal ecosystems world wide. These blooms are dominated typically by only one out of several co‐occurring opportunistic species, which are all favored by increased nutrient loads. We asked whether pronounced dominance of filamentous Pilayella littoralis Kjellm. (Phaeophyceae) over foliose Enteromorpha intestinalis L. (Chlorophyceae) in the Baltic Sea can be explained by interspecific physiological differences. In laboratory experiments, we analyzed uptake kinetics of nitrate, ammonium, and phosphate and the time dependency of uptake rates for both species. We further examined growth rates and nutrient assimilation in relation to single and combined enrichment with nitrate and phosphate, and three different nitrogen sources. Overall, we did not detect distinct differences in uptake, growth, and assimilation rates between P. littoralis and E. intestinalis. Minor differences and the related advantages for single species are discussed. Highest maximal uptake rates were found for ammonium, followed by nitrate and phosphate. Strong time dependency of uptake occurred, with the highest rates during the first 15 to 30 min. Nitrate enrichment had far more of an effect on growth than phosphate. Enrichment with urea, ammonium, and nitrate significantly increased growth rates without interspecific differences. A larger surface area to volume (SA/V) ratio in Pilayella compared with Enteromorpha did not translate into greater physiological capacity. We conclude that species dominance patterns in macroalgal blooms are not always a direct result of different ecophysiological traits among species. Ecological traits such as susceptibility to herbivory are important factors in determining species distribution in the field.