Biremis blandi (Polychaeta: Terebellidae), new genus,new species,caught by D.S.R.V. “Alvin” in the Tongue of the Ocean,new providence,Bahamas

Biremis, n. gen., characterized by an enlarged cephalic lobe, achaetous thoracic segments, and abdominal bilobed uncinigerous pinnules, lacks eyes and branchiae and is, thus, grouped with the subfamily Polycirrinae of the Terebellidae. Biremis blandi, n. sp., has prominent longitudinal muscular ventral ridges, lacking ventral glandular scutes. The avicular uncini, arranged in a single row on each lobe of each abdominal pinnule, are very similar to those of Polycirrus. The new species, collected from D.S.R.V. Alvin, was observed resting on and swimming over the sloping walls of the Tongue of the Ocean (25° N; 77°35 W), at 600 m depth. Its ability to swim may be a requirement for survival on an unstable substratum.Contribution No. 2891 from the Woods Hole Oceanographic Institution.     

Adaptation and equivalence in open-ocean phytoplankton

Two marine phytoplankton species of the North Atlantic Ocean have inherently differt growth responses to changing nutrient conditions. Yet they co-occur. Thus, they can be compared under the same conditions via equivalence, provided that their adaptedness is linked to their responsiveness as follows. If Species x is adapted to nutrient changes, then it is responsive to these conditions and, certainly, if it is responsive to these conditions, then it is adapted to them. There is another expression that is equivalent to this one (that says the same thing): either Species x is adapted and responsive to these conditions or it is neither adapted nor responsive to them. The option just mentioned is resolved so that Emiliania huxleyi as Species x is adapted and responsive and Cyclococcolithus leptoporus as Species x is not adapted and not responsive. All the frequently observed species in the winter half of the year, November to April, from 1961 to 1972 are like E. huxleyi in being adapted and responsive or like C. leptoporus in being unadapted and unresponsive.Contribution No. 5806 from the Woods Hole Oceanographic Institution     

Food size spectra,ingestion and growth of the copepodAcartia tonsa during development: Implications for determination of copepod production

Clearance rates on different sizes of spherically shaped algae were determined in uni-algal experiments for all developmental stages (NII through adult) of the copepodAcartia tonsa, and used to construct food size spectra. Growth and developmental rates were determined at 7 food levels (0 to 1 500 g C l^-1 ofRhodomonas baltica). The lower size limit for particle capture was between 2 and 4 m for all developmental stages. Optimum particle size and upper size limit increased during development from 7 m and 10 to 14 m for NII to NIII to 14 to 70 m and 250 m for adults, respectively. When food size spectra were normalized (percent of maximum clearance in a particular stage versus particle diameter/prosome length) they resembled log-normal distributions with near constant width (variance). Optimum, relative particle sizes corresponded to 2 to 5% of prosome length independent of developmental stage. Since the biomass of particulate matter is approximately constant in equal logarithmic size classes in the sea, food availability may be similar for all developmental stages in the average marine environment. Juvenile specific growth rate was exponential and increased hyperbolically with food concentration. It equaled specific female egg-production rate at all food concentrations. The efficiency by which ingested carbon in excess of maintenance requirements was converted into body carbon was 0.44, very similar to the corresponding efficiency of egg-production in females. On the assumptions that food availability is similar for all developmental stages, and that juvenile and female specific growth/egg-production rates are equal, female egg-production rates are representative of turnover rates (production/biomass) of the entireA. tonsa population and probably in other copepod species as well. Therefore, in situ estimates of female fecundity may be used for a rapid time- and site-specific field estimate of copepod production. This approach is shown to be fairly robust to even large deviations from the assumptions.     

Exosmosis and “free space” in marine benthic algae

In distilled water, marine benthic algae immediately lose ions. This can be demonstrated by means of chloride titration or conductivity measurements. The rapidity and the complete reversibility of this process show that ion movements out of and into the free space are involved. When Laminaria saccharina thalli, exposed to a series of increasing NaCl-concentrations, are subsequently transferred into distilled water, the external concentration increases proportionally to rate of ion loss. Through its free space, the alga establishes an ionic equilibrium with its external medium. If the alga thallus is killed (20 sec boiling in isosmotic sea water), the extent of chloride loss is much higher. Because of thermal destruction of the osmotic space, the chloride can then escape from the entirc thallus. Since sublittoral algae die upon drying, chloride loss from dry thalli is much higher than that from wet thalli: this difference is small in littoral algae, which tolerate short periods of dryness. A close relationship exists between extent of chloride loss and degree of resistance to drying.     

Alkanes and alkenes in marine benthic algae

Saturated and olefinic hydrocarbons were determined in additional species of benthic marine algae from the Cape Cod (Massachusetts, USA) area (see: Youngblood et al., 1971). The distribution of homologous and isomeric olefins was studied in plants of different age and in morphologically different parts of the same specimen. With two minor exceptions, only normal alkanes and alkenes are present. The methylene-interrupted C₁₉- and C₂₁-polyolefins are particularly abundant; ¹-heneicosahexaene and the corresponding pentaene are common to all brown algae, while the corresponding ³-isomers occur in green algae. The hydrocarbon concentration, the alkene-to-alkane ratio and the polyolefin content are highest in young plants or in rapidly growing tissues of older plants. This suggests a deeper involvement in cell biochemistry of straight-chain hydrocarbons than previously considered. The biosynthesis of the plant polyolefins remains to be explored; no immediately obvious precursors of the ¹-polyolefins were found among the algal fatty acids. The hydrocarbon composition of these benthic algae differs greatly from that of fossil fuels in its simplicity and predominately unsaturated nature. The separation of the isomers by gas chromatography and their structural elucidation by mass spectrometry, alone and in combination with hydrogenation and ozonolysis, are discussed.Contribution No. 3155 of the Woods Hole Oceanographic Institution.     

Selective particle ingestion by oyster larvae (Crassostrea virginica) feeding on natural seston and cultured algae

I investigated selective particle ingestion by oyster larvae (Crassostrea virginica) feeding on natural seston from Chesapeake Bay and laboratory-cultured algae of different sizes or chemical content. In 15 of 16 experiments with complex natural suspensions as food, small(<150 m) and large (>150 m) larvae selected most strongly for small (2 to 4 m) food particles, but in the presence of a large (>10 m)-cell dinoflagellate bloom, large larvae strongly selected much larger (22 to 30 m) food material (presumably dinoflagellates). When fed simplified mixtures of four cultured algal species (Synechococcus bacillaris, Isochrysis sp., Dunaliella tertiolecta, and Prorocentrum minimum) ranging in size from 1 to 11 m, small larvae preferred 1 m algae while large larvae preferred 11 m algae. In experiments with algal mixtures, and with suspensions of natural particles and added algae, large larvae preferred algal species harvested from exponential-phase cultures over other species from stationary-phase cultures. Larval ingestion rates of the cultured alga Thalassiosira pseudonana were about three times higher for cells with a low carbon:nitrogen ratio (7.2:1) than for high C:N ratio (16.2:1) cells when these cells were offered separately in suspensions of equal concentration. As a result, more algal cells, algal C, and algal N was ingested by larvae fed low C:N cells. However, larvae did not show a significant preference for either type of cell when they were offered in a 1:1 cell mixture. Feeding patterns of C. virginica larvae in natural food suspensions can vary with the composition of these complex suspensions, and ingestion seems dependent not only on the size, but on the growth rate and chemical quality of food particles.     

Discussion of methods of investigating the food of fishes,with reference to a preliminary study of the prey of Gobiusculus flavescens (Gobiidae)

The validity, reliability and practicability of different methods for the investigation of stomach contents of a small, plankton-eating fish are discussed. Tests demonstrated the problems related to mass and volume measurements of planktonic food. Several nutrition indices, particularly Hynes's frequency of occurrence are criticized. A logarithmic version of Shorigin's index is proposed as a replacement for Ivlev's food selection index. A preliminary study on the food of Gobiusculus flavescens (Fabricius), sampled in July, 1975 at Helgoland, provides some numerical information on the composition of its stomach contents and food preference.     

Suspension-feeding by herbivorous calanoid copepods: A cinematographic study

Many planktonic calanoid copepods are commonly described as filter-feeders. Direct observations using high-speed micro-cinematography indicate that these animals are suspension-feeders. They capture and handle the food particles not passively according to size and shape but, in most cases, actively using sensory inputs for detection, motivation to capture, and ingestion.     

Feeding,growth and bioluminescence of the heterotrophic dinoflagellate Protoperidinium huberi

Feeding, growth and bioluminescence of the thecate heterotrophic dinoflagellate Protoperidinium huberi were measured as a function of food concentration for laboratory cultures grown on the diatom Ditylum brightwellii. Ingestion of food increased with food concentration. Maximum ingestion rates were measured at food concentrations of 600 g C l^-1 and were 0.7 g C individual^-1 h^-1 (1.8 D. brightwelli cells individual^-1 h^-1). Clearance rates decreased asymptotically with increasing food concentration. Maximum clearance rates at low food concentration were ca. 23 l ind^-1 h^-1, which corresponds to a volume-specific clearance rate of 5.9x10⁵ h^-1. Cell size of P huberi was highly variable, with a mean diameter of 42 m, but no clear relationship between cell size and food concentration was evident. Specific growth rates increased with food concentration until maximum growth rates of 0.7 d^-1 were reached at a food concentration of 400 g C l^-1 (1000 cells ml^-1). Food concentrations as low as 10 g C l^-1 of D. brightwellii (25 cells ml^-1) were able to support growth of P. huberi. The bioluminescence of P. huberi varied with its nutritional condition and growth rate. Cells held without food lost their bioluminescence capacity in a matter of days. P. huberi raised at different food concentrations showed increased bioluminescence capacity, up to food concentration that supported maximum growth rates. The bioluminescence of P. huberi varied over a diel cycle, and these rhythmic changes persisted during 48 h of continuous darkness, indicating that the rhythm was under endogenous control.     

Incorporation and utilization of bacterial lipids in theSolemya velum symbiosis

We undertook a detailed analysis of the lipid composition ofSolemya velum (Say), a bivalve containing endosymbiotic chemoautotrophic bacteria, in order to determine the presence of lipid biomarkers of endosymbiont activity. The symbiont-free clamMya arenaria (L.) and the sulfur-oxidizing bacteriumThiomicrospira crunogena (Jannasch et al.) were analyzed for comparative purposes. The ¹³C ratios of the fatty acids and sterols were also measured to elucidate potential carbon sources for the lipids of each bivalve species. Both fatty acid and sterol composition differed markedly between the two bivalves. The lipids ofS. velum were characterized by large amounts of 18: 17 (cis-vaccenic acid), 16:0, and 16 : 17 fatty acids, and low concentrations of the highly unsaturated plant-derived fatty acids characteristic of most marine bivalves. Cholest-5-en-3-ol (cholesterol) accounted for greater than 95% of the sterols inS. velum. In contrast,M. arenaria had fatty acid and sterol compositions similar to typical marine bivalves and was characterized by large amounts of the highly unsaturated fatty acids 20 : 53 and 22 : 63 and a variety of plant-derived sterols. The fatty acids ofT. crunogena were similar to those ofS. velum and were dominated by 18:17, 16:0 and 16:17 fatty acids. Thecis-vaccenic acid found inS. velum is almost certainly symbiontderived and serves as a potential biomarker for symbiontlipid incorporation by the host. The high concentrations ofcis-vaccenic acid (up to 35% of the total fatty acid content) in both symbiont-containing and symbiont-free tissues ofS. velum demonstrate the importance of the endosymbionts in the lipid metabolism of this bivalve. The presence ofcis-vaccenic acid in all the major lipid classes ofS. velum demonstrates both incorporation and utilization of this compound. The ¹³C ratios of the fatty acids and sterols ofS. velum were significantly lighter (–38.4 to –45.3) than those ofM. arenaria (–23.8 to – 24.2) and were similar to the values found for the fatty acids ofT. crunogena (–45); this suggests that the lipids ofS. velum are either derived directly from the endosymbionts or are synthesized using endosymbiontderived carbon.Woods Hole Oceanographic Institution Contribution No. 7356Please address all correspondence and reprint requests to Dr Conway at her present address: Department of Biological Sciences, University of Pittsburgh, Pennsylvania 15260, USA     

Grazing and ingestion rates of nauplii,copepodids and adults of the marine planktonic copepod Calanus helgolandicus

The average grazing and ingestion rates of all stages of the marine planktonic copepod Calanus helgolandicus (Calanoida) from nauplius stage IV to adults were measured experimentally at 15°C in agitated cultures. The chain-forming diatom Lauderia borealis and the unarmoured dinoflagellate Gymnodinium splendens were offered as food. The food concentrations were close to natural conditions and ranged from 36 to 101 g of organic carbon per liter. The medium body weights expressed in g of organic carbon of almost all larval stages raised at 49 g C/1 were identical with the weight of the same stages caught in the Pacific Ocean off La Jolla, California, USA. In a log-log system, grazing and ingestion rates increased almost linearly with increasing body weight. Grazing rates ranged from 4 to 21 ml/day/nauplius stage IV to 286 ml to 773 ml/day/female. Ingestion rates increased from 0.2 g to 0.8 g C/day/nauplius stage IV to 18 g to 69 g C/day/female. Grazing and ingestion rates per unit body weight decreased gradually with increasing body weight. The daily ingested amount of food decreased from 292 to 481% of the body weight (g C) of nauplius stage V to 28–85% of the body weight of adult females. Grazing and ingestion performances of all stages increased with increasing particle size. Grazing rates decreased and ingestion rates increased with increasing food concentrations. The published data on food intake of the different age groups of C. helgolandicus show that the young stages of herbivorous planktonic copepods can play a major part in the consumption of phytoplankton in the sea due to their high grazing and ingestion rates.     

The effect of male calling on female locomotor activity of Teleogryllus commodus

Summary The calling song of the -cricket, Teleogryllus commodus, attracts for mating. Both calling and -locomotor activity are under circadian control and the behaviors occur approximately at the same time. Daily playback of calling songs for 3–12 h in constant light failed to entrain -running. Instead, calling acts as an external stimulus which can release -locomotion at any time of the 24-h period, while the clock-induced activity continues to run freely. The stimulatory effect of the calling song causes flexible extension of -locomotor activity, but a subsequent restorative period is necessary. The ecological consequences of acoustical stimulation are discussed.     

Distribution of algae on tropical rocky shores: spatial and temporal patterns of non-coralline encrusting algae in Hong Kong

Encrusting algae have been described as dominant space occupying species on rocky shores around the world. Despite their abundance, however, most studies classify species under generic names (e.g. Ralfsia sp.) or as a functional group (e.g. encrusting algae), thereby underestimating the number of species present and their ecological importance. Studies on six rocky shores of varying exposure, in Hong Kong, recorded eight common species of encrusting algae. The greatest abundance of encrusting algae was recorded on shores of intermediate exposure, where four distinct zonation bands could be identified; a cyanobacterial Kyrtuthrix-Zone in the upper midlittoral, a Bare-Zone below this, a Mixed-Zone in the lower midlittoral and a Coralline-Zone in the infralittoral fringe. Abundance declined on shores of greater and lower exposure to wave action, where bivalves and barnacles were competitively dominant. Certain species were found in greater abundance on exposed shores (e.g. Dermocarpa sp. and Hildenbrandia occidentalis), while others preferred more sheltered shores (e.g. Hildenbrandia prototypus and Kyrtuthrix maculans). With the exception of some cyanobacterial crusts, the abundance of encrusting algae was always greatest towards the low shore, an area of decreased physical stress and increased herbivore density. Zonation patterns showed seasonal variation associated with the monsoonal climate of Hong Kong. Most species increased in abundance during the cool season, while during the summer months the cover and vertical extent of encrusting algae decreased in relation to summer temperatures, although K. maculans increased in abundance during the summer. On Hong Kong shores, encrusting algae have a high species richness and exhibit within-functional group spatial and temporal variation which is mediated by herbivory and seasonal, physical stresses.     

13C/12C ratios and the trophic importance of algae in Florida Syringodium filiforme seagrass meadows

Over 380 stable carbon isotope (¹³C) analyses made during 1981–82 showed that Syringodium filiforme Kutz seagrass meadows in the Indian River lagoon of eastern Florida have food webs based on algal rather than seagrass carbon. Seagrasses averaging approximately-8 were isotopically distinct from algae epiphytic on seagrass blades (X=-19.3) and particulate organic matter in the water column X=-21.6. ¹³C values of most fauna ranged between-16 and-22, as would be expected if food web carbon were derived solely from algal sources. These results counter the idea that seagrass detritus is the dominant carbon source in seagrass ecosystems. Two factors that may contribute to the low apparent importance of seagrass in the study area are high algal productivities that equal or exceed S. filiforme productivity and the high rates of seagrass leaf export from meadows.     

Production and role of hyaline hairs in Ceramium rubrum

Light intensity within the range of 40 to 210 E · m^-2 · s^-1 had relatively little effect on the abundance, length or distribution of Ceramium rubrum unicellular, hyaline hairs. External NH ₄ ⁺ concentrations less than 0.5 M stimulated hair initiation and growth in apical regions of the thalli. Ammonium concentrations in excess of 20 M inhibited hair formation on all regions of the thalli. Ammonium uptake velocities of plants with hairs were approximately twice those of plants without hairs. These hairs may be adaptive to take advantage of intermittent bursts of nutrients by increasing the plant's surface area and, hence, the number of nutrient uptake sites.Woods Hole Oceanographic Institution Contribution No. 5526     

Nutrition studies in the nauplius larva of Calanus pacificus (Copepoda: Calanoida)

Nauplii of Calanus pacificus were raised on a mixture of algae. Details of the mouth-parts, such as denticles, labial palps and lobes, setations and structure of the masticatory teeth were examined by scanning electron microscopy (SEM). Under the experimental conditions (15°C and 300 gC l^-1), exponential growth coefficients for the period Nauplii II–VI were 0.179 for carbon and 0.228 for nitrogen. C:N ratios dropping from 5.1 to 4.7. Growth was isochronous, each stage lasting 1.5 days. Respiratory losses were 15 to 19.6% of body carbon daily. Nauplii raised on a given alga showed higher rates of ingestion in the presence of this food, compared to nauplii switched to other algae. Minimal threshold concentrations for feeding were found, depending on the size of the food offered and ranging from 5.8 gC I^-1 for Lauderia borealis (28.7 m spherical diameter) to 47.1 gC 1^-1 for Chlamydomonas sp. (11.0 m). Unlike the Copepodite I stage, Nauplii II–VI larvae were not able to ingest small cells such as Isochrysis galbana (4.3 m), or very large ones such as Ditylum brightwellii (47.5 m) at more than maintenance rations. Below the critical concentration for maximal feeding, ingestion was clearly dependent on size of the cells offered, but the size-dependent relationship was different for diatoms and non-diatoms. Filtering rates increased from a threshold concentration to a maximal rate at about 50 gC 1^-1, and decreased at higher concentrations. Critical concentrations ranged from 125 gC 1^-1 for L. borealis to 1000 gC 1^-1 for Chlamydomonas sp. Maximal daily rations ranged between 100 and 150% of body carbon.     

Elemental composition (C,N,H) in larval and crab-1 stages of Pagurus bernhardus (Decapoda,Paguridae) and Carcinus maenas (Decapoda,Portunidae)

Analyses of individual content of carbon (C), nitrogen (N), and hydrogen (H) were carried out for all larval stages of Pagurus bernhardus and Carcinus maenas, and for newly metamorphosed crabs. Maximum range in total larval development is 12.8 to 165.8 g C, 3.2 to 35.1 g N, and 1.9 to 24.9 g H in P. bernhardus and 3.1 to 43.2 g C, 0.7 to 10.1 g N, and 0.4 to 6.3 g H in C. maenas. From these data energy equivalents were calculated. Maximum range in total larval life is 0.43 to 6.38 J ind. ^-1 in P. bernhardus and 0.1 to 1.49 J ind. ^-1 in C. maenas. There is a 32.4% mean loss of energy in P. bernhardus megalopa development; this seems to describe the normal developmental pattern in this stage. Biomass was determined as fresh and dry weight respectively. Individual dry weight is about 3.6 to 5.6 times higher in P. bernhardus (44 to 340 g) than in C. maenas (12 to 93 g) larvae.Contribution to research project Experimentelle marine Ökosystemanalyse sponsored by Bundesministerium für Forschung und Technologie, Bonn (Grant No. MFU-0328/1)     

Salinity tolerance of benthic estuarine diatoms as tested with a rapid polarographic measurement of photosynthesis

Measurements of net photosynthesis of benthic estuarine diatoms were made by polarographic registration of oxygen saturation. A measuring cell was constructed in which media with salinities of 2.0 to 100.7 were pumped over the algae between measurements. Diatoms from unialgal cultures and mixed populations from intertidal flats appeared to be highly tolerant of extreme salinities. During short-term exposures (20 min) the net photosynthesis of the algae did not drop below 70% of the initial values, within the salinity range 4.0 to 60.0. Prolonged exposure (up to 6 h) gave essentially the same results. Populations of benthic diatoms, sampled from field stations with mean salinities of about 30, 12, and below 5, showed only gradual differences in their tolerance of salinities between 2.0 and 33.7. Two species, Navicula arenaria and Nitzschia sigma, were cultured in media ranging in salinity from 8.0 to 45.0 and from 2.0 to 45, respectively. The tolerance to changing salinity was only slightly affected by the salinity of the medium in the preculture. The role of salinity in the production and distribution of intertidal diatoms is discussed.     

Biological effects of surface active agents on marine animals

The biological effects of 5 surface active agents (the anionic ABS, LAS and LES 3 EO and the nonionic NP 10 EO and TAE 10 EO) on marine fishes, crustaceans and bivalves have been tested in, continuous-flow systems. Concentrations from 100 to 0.5 ppm were normally used. Fishes were found to be more susceptible (96 hLC 50 range: 0.8 to 6.5 ppm) than bivalves (96 hLC50 range: 5 to >100 ppm) while crustaceans were considerably more resistant (96 h LC 50 range: 25 to > 100 ppm). Within each of these 3 systematic groups, more active species were found to be more sensitive than less active species. Developmental stages were also more sensitive than adults. The resistance of crustaceans to surfactants decreases immediately after moulting. The most toxic agent for fishes and decapods was the soft anionic LAS, and for bivalves and barnacles the hard nonionic NP 10 EO. Ability to recover normal behaviour after exposure decreases with increasing concentration and time, and ceases earlier in anionic than in nonionic surfactants. The first reaction to the surfactants is increased activity (avoidance reaction of mobile species), followed successively by inactivation, immobilization and death. Nonionic surfactants affect the equilibrium in fishes. Sublethal effects appear as impaired locomotory activity and breathing rate in fishes and crustaceans, impaired byssus activity and shell closure in Mytilus edulis, burrowing in Cardium edule, Astarte montagui and Astarte sulcata. Siphon retraction is affected in Mya arenaria and Cardium edule, as is also the response to food of the Leander spp.     

Settlement of larvae of the giant scallop,Placopecten magellanicus,in 9-m deep mesocosms as a function of temperature stratification,depth, food,and substratum

In January and February 1992 an experiment was conducted in a 10.5-m deep tank (diameter: 3.7 m, volume: 117 m³) to examine the effects of food distribution with respect to a stable thermocline, depth, and substratum type on the settlement and metamorphosis of larvae of the giant scallop, Placopecten magellanicus (Gmelin). Polyethylene tube bags (diameter: 0.60 m) were used to enclose 9-m deep columns of seawater which were then used as treatment replicates. A sharp thermocline (i.e. 7 to 11°C gradient) was created between a depth of 4.0 and 5.0 m. At the beginning of the experiment, one million 6-d old larvae were added to the surface of each tube. Two or three replicate tubes of each of four feeding treatments were established: (1) food (Isochrysis galbana) added to the top 1 m of the water column (top-fed, n=3); (2) food added to the bottom 1 m of the water column (bottom-fed, n=3); (3) food added throughout the water column (mixed, n=3); and (4) no food added (unfed, n=2). Settlement collectors were placed in two replicate tubes of each treatment at depths of 0.1, 4, 5, and 9 m and contained two different substrata, Polysiphonia lanosa (a red filamentous alga) and aquarium filter-wool as an algal mimic. Spat settlement in the different feeding treatments was a function of larval growth rate. Most spat were collected in the mixed tubes. Fewer individuals were collected in the top-fed treatment and fewer still in the bottom-fed treatment; minimal numbers of spat were found in the unfed tubes. Filter-wool collected more spat than P. lanosa, but this was evident only in the 4-m deep collectors in the mixed tubes. Most spat were found in the 0.1-m or 4-m deep collectors; generally few were located below the thermocline in collectors at 5 or 9 m. We suggest that, in areas of intense stable stratification, spat collection of the giant scallop may be enhanced by the placement of collectors with appropriate substratum material at or above the zone of stratification, rather than near the bottom. Furthermore, we propose that natural settlement may be increased in areas where a stratification layer intersects with the sea floor or where the layer is disrupted by turbulent mixing.Contribution to the programs of OPEN (Ocean Production Enhancement Network, one of the 15 Networks of Centres of Excellence supported by the Government of Canada) and GIROQ (Group Interuniversitaire de Recherches Océanographiques du Québec)