ALBERT

Description: A number of reproductive indices were compared with a subjective maturity scale for assessment of Loligo forbesi maturity. The ratio between nidamental gland length and mantle length corresponded well with female maturation, as did the ovary mass-soma mass and nidamental gland mass-soma mass ratios. For males, the ratio between spermatophoric complex mass and somatic mass was found to be the most suitable for maturity assessment. The timing of recruitment and maturation of L. forbesi in Irish waters was described from the size and maturity of squid in commercial landings in the south of Ireland during the years 1991–1993. Immature squid first appeared in commercial catches in July and August, and this represented the main period of recruitment. A second period of recruitment was apparent in December 1991, but was not identified in the 1992–1993 season. Mature females were present in the commercially exploited population between November and April, with a small number also found in the summer. The abundance of egg masses was used to indicate timing of spawning. Egg masses recovered from the Cork coast indicated that peak spawning occurred during the winter months, but continued on a small scale for much of the year.

Description: Statolith morphology and microstructure were studied in two common species of panktonic cranchiid squids, Belonella borealis [four juveniles with mantle length (ML) 375–450 mm] and Galiteuthis phyllura (13 paralarvae and juveniles, ML 9–235mm), caught near the bottom and in pelagic layers over the continental slope of Siberia in the northwest Bering Sea. The total number of growth increments within the statoliths ranged from 277 to 294 in B.borealis and from 10 to 209 in G.phyllura. Assuming that these increments were produced daily, both species grow rapidly in length (daily growth rate = 1.13mm day−1 during the first 8–10 months of their juvenile phase in the mesopelagic layers, prior to migration into deeper waters for maturation.

Description: The ECM of astrocytic tumors promotes and modulates a variety of cell functions, such as cell attachment, migration, proliferation, survival, and signaling. Recent studies indicate that there are extensive and complex interactions among ECM molecules and that these can modify the function of the participating molecules, interactions between the proteoglycan, phosphacan, and the ECM protein, tenascin, being an example (63). In addition, on nonastrocytic cell types it has been shown that an integrin receptor and the cell surface proteoglycan CD44 recognize the same ECM ligand osteopontin, and thus modulate each others function (77, 86). Thus, interacting components in the ECM and cell surface receptors likely cooperate in regulating cell function and tumor invasion (59, 77, 80, 85-87, 95). As tumor cells are capable of remodeling their ECM through synthesis of ECM proteins and proteoglycans, as well as upregulating integrin receptors and proteoglycans on their cell surface, tumor cells are capable of controlling their own destiny. ECM molecules which are concentrated in blood vessels of malignant astrocytomas, such as tenascin-C and the 250-kDa CSPG (NG2), are potentially therapeutic targets.

Description: A total of 103 cephalopod paralarvae were sampled during June 1995 in Galician waters (NW Spain). Samples were taken with Bongo nets of 300 and 500 〈IMG SRC="/math/mu.gif"〉m mesh size at 48 sampling stations along 10 transverse transects ranging from 80 to 600 m water depth. Paralarvae of loliginid squid were most abundant (40%). The〈it〉Rhynchoteuthion〈/it〉 paralarvae of ommastrephid squid accounted for 25%, whereas sepiolids comprised 23% of the total sample. Octopods were scarce, at only 6.6%. Other cephalopod families accounted for 5%. Sizes of paralarvae ranged from 1.0 to 7.1 mm mantle length. Temperature and salinity distribution showed the presence of an intense upwelling during the survey period. The sampling data obtained before and during the presence of upwelled water off Rias of Pontevedra and Vigo (southern zone) showed that paralarval cephalopod abundance and distribution were closely related to the upwelled Eastern North-Atlantic Central Water (ENACW).

Description: This paper discusses an observing system simulation experiment which reveals the difference in primary production of (i) phytoplankton moving freely in the turbulent mixed layer of the upper ocean and (ii) a sample of the same population held in a bottle at fixed depths. The results indicate the tendency of incubation measurements to overestimate phytoplankton production rates by up to 40%. Differences in primary production depend to a first approximation on the vertical extent of mixing and on water turbidity. A simple model was constructed leading to a non-linear calibration function which relates the difference in primary production to surface irradiance, mixing depth and to the depth of the euphotic zone. This function has been applied to calibrate the production rates simulated at fixed depths, and the corrected values were verified by comparisons with productivities in the turbulent environment. The calibration function was found to be capable of reducing the differences significantly.

Description: One of the critical issues in large-scale physical/biological coupled models is the survival of zooplankton in a water column circulating an anticyclonic gyre. Survival is most at risk in regions where the phytoplankton food supply is low due to environmental stress by light-limitation (deep mixing in winter) or nutrient limitation (oligotrophy). To investigate this problem we simulated the ecosystem in a 1 m2 cross-section water column, using the Lagrangian Ensemble method in which plankton are treated as particles following independent trajectories through the changing environment. In this first part of a two-part article we report the results of simulating the ecosystem in a water column located off the Azores, where winter mixing reaches 200 m and there is seasonal, but not permanent oligotrophy. The model features diatoms and herbivorous copepods subject to carnivorous predation, with remineralization of carbon and nitrogen by bacteria attached to detritus and faecal pellets. The copepods become extinct after failing to reproduce in years of low food supply. We show that the risk of extinction can be reduced by allowing cannibalism or by reducing carnivorous predation; we discuss other possibilities: enhancing the food supply by adding new guilds of phytoplankton, and relaxing oligotrophy by allowing other sources of nitrogen injection into the euphotic zone.

Description: The potentially toxic diatom Pseudonitzschia pungens f. multiseries was grown on different sources of nitrogen in batch cultures. Ammonium did not support growth at concentrations 〉200 μM, and even lowered the growth rate, when it was supplied in addition to growth-saturating nitrate concentrations. This seemed to be a combined effect of inhibition of nitrate uptake and direct ammonia toxicity. Urea, glutamine and nitrite were used readily by P.pungens.

Description: The seasonal development of oxygen concentrations in the deep water of a nearly permanently stratified station in Kiel Eight, which originates from inflows through the Great Belt and the Kattegat, was investigated. The bottom-water oxygen situation of an individual year was characterized by the apparent oxygen consumption rate from day 80 to day 260. The estimated consumption is poorly correlated with pelagic variables measured during the same year (winter-nutrient concentrations, DON, primary productivity, etc.). For the period 1979-1996, a significant correlation was found between oxygen consumption and average precipitation during the preceding 8 months (June-January). It is suggested that a considerable part of the production is transferred into the next year as particulate organic pool accumulated in, or on top of, the sediment rather than being immediately recycled.

Description: Trace elements and Sr–Nd–Pb isotopes have been analyzed on sedimentary and igneous (metabasalt, metadiorite and metagabbro) samples from the Jurassic oceanic crust beneath Gran Canaria (Canary Islands). The igneous crust exhibits extreme heterogeneity in 87Sr/86Sr (0.7029–0.7052), 206Pb/204Pb (18.2–20.8) and 208Pb/204Pb (38.1–41.3). Leaching experiments indicate that seawater alteration has elevated the 87Sr/86Sr ratio but has not appreciably affected 143Nd/144Nd (0.51295–0.51306). An Sm–Nd isochron gives an age of 178 ± 17 Ma, which agrees with the age predicted from paleomagnetic data. Hydrothermal alteration near the ridge axis has increased 207Pb/204Pb (15.59−15.73), 208Pb/204Pb (as well as Δ7/4Pb and Δ8/4Pb), 238U/204Pb (μ) and Ce/Pb but has not appreciably changed 206Pb/204Pb. The large range in 206Pb/204Pb and 208Pb/204Pb reflects radiogenic ingrowth with μ being as high as 107. Portions of the Jurassic ocean crust have trace element and isotope characteristics within the range found at St Helena, the Atlantic type locality for the HIMU (high μ) mantle end-member. Evaluation of the published isotopic data for Gran Canaria volcanic rocks indicates that the isotopic composition of these melts primarily represents the composition of their mantle sources rather than crustal assimilation.

Description: Osmium concentrations and isotopic signatures were measured in 28 primarily Holocene basalts (22 of which have been analyzed for Sr–Nd–Pb isotope composition), two carbonatites and two mantle xenoliths from the Canary Islands, Selvagen Grande and Madeira in the eastern North Atlantic. 187Os/188Os ratios in the basalts range from 0.129 to 0.183. The Os isotope systematics indicate that the basalts fall into three petrogenetic groups: (1) a ‘radiogenic’ group with high 187Os/188Os from 0.152 to 0.183; (2) an ‘unradiogenic’ group with low 187Os/188Os from 0.129 to 0.138; (3) an ‘intermediate’ group with 187Os/188Os between 0.139 and 0.151. The Os isotope systematics of the radiogenic group samples are consistent with minor contamination of the basalts by marine sediment. All samples in the unradiogenic group contain mantle xenoliths, and the unradiogenic Os can be explained by bulk assimilation of ≤ 5% mantle peridotite in the form of disaggregated xenoliths. The radiogenic and unradiogenic groups are also characterized by higher 87Sr/86Sr and 208Pb/204Pb but lower 143Nd/144Nd than samples with similar 206Pb/204Pb from the intermediate group, which is interpreted to reflect interaction of plume magmas with the lithospheric mantle. The intermediate group samples are believed to represent the isotopic signature of the mantle plume. The Os isotopic composition of the Canary plume is among the most radiogenic found in ocean island basalts, comparable with the endmember HIMU islands Mangaia and Tubuaii, but at significantly lower 206Pb/204Pb. The radiogenic Os and moderate 206Pb/204Pb signature of the Canary plume is consistent with a plume which contains 25–35% of relatively young (∼1.2 Ga) recycled oceanic crust. Variable degree of mixing of the Canary Island plume source with shallow depleted asthenosphere containing a component of Paleozoic oceanic crust produces the limited range in Os isotopic signatures observed in the Madeira and Canary Island basalts despite a large range in 206Pb/204Pb isotopic composition.

Description: Statolith microstructure was studied in hatchlings of deepwater-spawned gonatid squid Gonatus onyx, caught between 1350 and 1420 m over a bottom depth of 2100 m in the San Clemente Basin off San Diego, California. It was found that the shape and size of the hatchling statolith were similar to those of the first-check statolith observed in paralarvae and small juveniles of G.onyx. The inner part of the bipartite postnuclear zone (= first-check statolith) is formed during late embryo-genesis, and the first check within the statolith microstructure must be considered as a starting point of increment counting for age estimation of Gonatus

Description: Length–frequency analysis was employed to resolve multiple cohorts in the Loligo forbesi population from coastal waters to the west of Scotland. In both male and female squid two principal cohorts were identified, recruiting to the fished population in April and November. Both cohorts spawned during the winter months (November to April), producing a single extended spawning season, with the April recruits of larger size at spawning than the November recruits. In the males the April recruits appeared to separate into two cohorts of different growth rates, thus producing three rather than two sizes at maturity. The abundance of L. forbesi was low during the summer months, indicating that the squid had moved outside the range of the fishery, perhaps into deeper water. Abundance declined during the spawning season, which is interpreted as post-spawning mortality. Abundance declined earlier in the males than females, producing a female biased sex ratio during most of the spawning season. The two periods of recruitment are not compatible with a 1 year life cycle and single extended spawning season and explanations of this are discussed.

Description: Findings from experiments showed that the web-feeding euthecosomatous pteropod, Limacina retroversa, can produce rapidly sinking, mucous aggregates. It is suggested that, by adhesion, these aggregates scavenged picoplankton-sized particles, which were thus effectively cleared from the medium. In contrast, Calanus finmarchicusw as not able to clear these particles in our experiments. Sedimentation velocities of 10 aggregates measured in vivo were up to 1000 m day1, with an average of —300 m day-1 (not including two aggegates with neutral buoyancy). Mean velocities measured for feces of C.finmarchicus, Calanus hyperboreus and Thysanoessa sp. were considerably lower. We suggest that the sedimentation of L.retroversa aggregates was the source of mucous floes collected in sediment traps (Bathmann et al., Deep-Sea Res., 38,1341-1360,1991) and at the sea floor at 1200 m depth in the southern Norwegian Sea. This process may be an important mediator of sedimentation to the deep sea, when these pteropods are present in surface waters in large abundance.

Description: The impact of nutrient supply ratios on the functional geometry of phytoplankton has been studied by means of competition experiments with phytoplankton communities from the Arabian Sea. Cell length and deviation from spherical shape of dominant competitors increased with Si:N ratios.Surface:volume ratios were minimal at intermediate Si:N ratios. Grazing by the rotifer Brachionus plicatilis did not lead to a qualitative shift in the response of geometric properties to Si:N ratios; however, mean cell lengths increased while surface:volume ratios decreased.