Diel changes in phytoplankton photosynthetic efficiency in Brackish waters

From 18 to 23 September 1974, investigations on the diel changes in phytoplankton were carried out in the Baltic Sea. Every 4 h, water samples were collected from 2 and 15 m, and PO₄, chlorophyll a, temperature, salinity, pH, phytoplankton composition and phytoplankton light photosynthesis relationship were determined. Continuous measurements of surface irradiance and some estimations of zooplankton were also made. P ^B (photosynthesis per unit chlorophyll a at low light levels of 2·10^-2 cal cm^-2 min^-1) revealed only random variation during the sampling period, i.e., 1.0 to 1.6 mg C (mg chlorophyll a)^-1 h^-1. P _m ^B (Light-saturated photosynthesis per unit of chlorophyll a) displayed pronounced diel fluctuations with the highest value of about 6 mg C (mg chlorophyll a)^-1 h^-1 around noon, and the lowest value of about 2.5 mg C (mg chlorophyll a)^-1 h^-1 during the night, during which latter period the value of P _m ^B was more or less constant. Reasons for the diel fluctuations are discussed, and an equation which describes these fluctuations is proposed. Using this equation, the daily phytoplankton production estimated in incubators by a previously described method can be corrected for the time of day at which samples are collected.     

Aspects of water column primary productivity in the Chukchi Sea during summer

Measurements of primary productivity, chlorophyll a, incident solar radiation, phosphate-P, silicate-Si, nitrate-N, nitrite-N, ammonium-N, temperature and salinity were made in the Marginal Ice Zone of the Chukchi Sea in summer 1974. Low to moderate levels of primary productivity (0.07 to 0.97 g C m^-2 half-day^-1) were observed; primary productivity exceeded 3 g C m^-2 half-day^-1 at two stations. Surface primary productivity was nitrogen-limited at most stations. Mean chlorophyll a concentration in the photic zone varied from 0.4 to 17.8 mg m^-3. Higher concentrations and significant subsurface accumulation of chlorophyll a, reaching 40 mg m^-3, were observed in July at stations near the ice-edge than those in open water. No chlorophyll maximum was noted in September, when values ranged from 0.4 to 2.2 mg m^-3. It is postulated that the contribution of sea-ice algae to the total chlorophyll content can be substantial, but that the stay of these cells in the water column may not be long. Non-linear regression estimates from solar radiation and chlorophyll-specific primary productivity data showed a maximal photosynthetic rate of 18 mg C mg chlorophyll a ^-1 half-day^-1, an optimal light intensity of 54 langleys half-day^-1, and markedly reduced primary productivity at moderately higher light intensities. These features indicate that phytoplankton was shade-adapted.     

Studies of primary productivity in coastal waters of southern Long Island,New York

Phytoplankton productivity of the tidal estuaries and coastal waters of southern Nassau Country, Long Island, New York, USA was determined monthly at 28 stations during 1966. Diatoms alternated with dinoflagellates in dominating the standing crop in the coastal area. The estuaries were characterized by sustained blooms of green flagellates and dinoflagellates during the spring/summer period, 1966. Chlorophyll a ranged from 1.0 to 27.6 mg/m³ in the estuarine area, and 1.45 to 10.15 mg/m³ in adjacent coastal waters. Rate of phytosynthesis per unit weight chlorophyll a for surface samples in the region under study a veraged from 3.1 to 3.5 mgC/mg chlorophyll a/h. At light saturation, however, the ratio varied according to water temperature and species' composition. Primary productivity decreased seawards, with mean values for 1966 of 0.35, 0.22, and 0.16 gC/m³/d for the estuarine, nearshore and offshore areas, respectively.This study was carried out at the Lamont Geological Observatory of Columbia University Palisades; New York, USA.The study was conducted with financial assistance from Nassau County, New York, and the G. Unger Vetlesen Foundation.     

Population genetic structure of the brown tiger prawn, Penaeus esculentus, in tropical northern Australia

Eight polymorphic microsatellite loci were analysed in six population samples from four locations of the Australian endemic brown tiger prawn, Penaeus esculentus. Tests of Hardy–Weinberg equilibrium were generally in accord with expectations, with only one locus, in two samples, showing significant deviations. Three samples were taken in different years from the Exmouth Gulf. These showed no significant heterogeneity, and it was concluded that they were from a single panmictic population. A sample from Shark Bay, also on the west coast of Australia, showed barely detectable differentiation from Exmouth Gulf (F _ST = 0 to 0.0014). A northeast sample from the Gulf of Carpentaria showed low (F _ST = 0.008) but significant differentiation from Moreton Bay, on the east coast. However, Exmouth Gulf/Shark Bay samples were well differentiated from the Gulf of Carpentaria/Moreton Bay (F _ST = 0.047–0.063). The data do not fit a simple isolation by distance model. It is postulated that the east–west differentiation largely reflects the isolation of east and west coast populations that occurred at the last glacial maximum when there was a land bridge between north-eastern Australia and New Guinea.     

Seasonal and areal changes in standing stocks of phytoplankton,zooplankton and micronekton in the eastern tropical pacific

Five standing stocks were measured together at similar latitudes and longitudes on seasonally repetitive cruises in 3 areas — western, eastern, and southern — of the eastern tropical Pacific. The stocks were chlorophyll a at 0 to 150 m depth (mg/m²), night and day zooplankton at 0 to 200 m depth (ml/1000 m³), and night crustacean micronekton and fish-pluscephalopod micronekton at 0 to 200 m depth (ml/1000 m³). The logarithms of the measurements of each stock in each area were subjected to analysis of variance with the following factors: season (2 month period), latitude, and longitude. Seasonal coverage was most comprehensive, with 7 successive periods, in the western area (approximately 16° N to 3° S latitude, 100° to 122° W longitude). Most stocks in most parts of the western area had a simple seasonal cycle of low amplitude, with a single maximum and minimum that usually differed by a factor <2; some stocks in some parts of the area exhibited no seasonal cycle; all statistically significant cycles, except for fish-plus-cephalopod micronekton, were similar in phase. In the other two areas, located broadly to the east and south of the western area, suitable measurements were made at only 2 periods (opposite seasons) of the year. There were indications of phase differences between chlorophyll a and zooplankton in the eastern area, which should be further investigated. Most standing stocks declined gradually from east to west, and were higher in known upwelling areas and areas of shoal thermocline than elsewhere.     

Spring sea ice photosynthesis,primary productivity and biomass distribution in eastern Antarctica, 2002–2004

While it is known that Antarctic sea ice biomass and productivity are highly variable over small spatial and temporal scales, there have been very few measurements from eastern Antarctic. Here we attempt to quantify the biomass and productivity and relate patterns of variability to sea ice latitude ice thickness and vertical distribution. Sea ice algal biomass in spring in 2002, 2003 and 2004 was low, in the range 0.01–8.41 mg Chl a m⁻², with a mean and standard deviation of 2.08 ± 1.74 mg Chl a m⁻² (n = 199). An increased concentration of algae at the bottom of the ice was most pronounced in thicker ice. There was little evidence to suggest that there was a gradient of biomass distribution with latitude. Maximum in situ production in 2002 was approximately 2.6 mg C m⁻² h⁻¹ with assimilation numbers of 0.73 mg C (mg Chl a)⁻¹ h⁻¹. Assimilation numbers determined by the ¹⁴C incubations in 2002 varied between 0.031 and 0.457 mg C (mg Chl a)⁻¹ h⁻¹. Maximum fluorescence quantum yields of the incubated ice samples in 2002 were 0.470 ± 0.041 with E _k indices between 19 and 44 μmol photons m⁻² s⁻¹. These findings are consistent with the shade-adapted character of ice algal communities. In 2004 maximum in situ production was 5.9 mg C m⁻² h⁻¹ with an assimilation number of 5.4 mg C (mg Chl a)⁻¹ h⁻¹. Sea ice biomass increased with ice thickness but showed no correlation with latitude or the time the ice was collected. Forty-four percent of the biomass was located in bottom communities and these were more commonly found in thicker ice. Surface communities were uncommon.     

Day-night differences in the emergence of demersal zooplankton from a sand substrate in a kelp forest

Day-night differences in abundance and biomass of demersal zooplankton in the water column were determined by trapping these animals as they emerged from the sand substrate in a kelp forest (Macrocystis pyrifera) ecosystem off Santa Catalina Island, California, USA. The day and night sampling periods of the 24 June 1979 new moon each lasted 12 h. Abundance and biomass of total demersal zooplankton were significantly higher in night samples. A mean of 2,425±1,168 demersal zooplankton m^-2 24 h^-1 migrated over a diel cycle; 97% of these animals were crustaceans. The mean biomass of demersal zooplankton was 94.2±27.6 mg ash-free dry wt m^-2 24 h^-1. No significant differences were found in either the abundance or biomass of demersal zooplanktion collected in low and high traps, suggesting that most animals collected 25 cm off the bottom can sustain swimming to at least 75 cm and that both traps give comparable estimates of the amount of demersal zooplankton available to planktivorous predators.     

Correlation of primary production as measured aboard ship in Southern California Coastal waters and as estimated from satellite chlorophyll images

Chlorophyll images suitable for the regional analysis of the Southern California Bight were obtained by satellite (Nimbus-7 Coastal Zone Color Scanner) on 27 February, 6 March and 11 March 1979. An algorithm to convert satellite chlorophyll data to primary production has been developed. In addition, primary production was measured along with other biological and physical factors from ships cruising in the Southern California Bight during late February and early March 1979. There was fair agreement between shipboard measurements and satellite estimations; for example, primary production (mg carbon m^-2 d^-1) averaged 554 mg from shipboard measurement and 403 mg from satellite estimation when averaged for the entire Bight for the course of the study. The high standard error associated with the variance in productivity index used in our algorithm prevented more accurate conversion of chlorophyll concentrations into primary productivity. However, the synoptic data provided by concurrent ship and satellite measurements can be used to quantify, and perhaps reduce, sampling errors associated with ship sampling alone and to provide estimates of the accuracy of primary productivity on a regional basis.     

Seasonal composition of meroplankton and holoplankton in the Bristol Channel

A decreasing gradation in the plankton standing stock of the Bristol Channel was observed from the seaward section to the inner, less saline, reaches. Two sub-regions of our survey, the North Outer Channel (NOC) and the Inner Channel (IC), represented the extremes of this gradient and were selected for detailed comparison. The integrated zooplankton biomass, over the 307 d sampling period (4 November 1973 to 6 September 1974), was 2 475 mg C m^-3 (266 mg C m^-2 d^-1) in the NOC and 335 mg C m^-3 (20 mg C m^-2 d^-1) in the IC. The omnivorous plankton accounted for 76% of the standing stock in the NOC and 89% in the IC, of which 58 and 23% were meroplankton and 39 and 71% were holoplankton, respectively; the remainder was unassigned. The majority of the meroplankton in both subregions was decapod larvae and adults, whereas the holoplankton biomass was dominated in the NOC by copepods (89%) and in the IC by mysids (57%), mainly Schistomyzis spiritus. Centropages hamatus was the most abundant copepod species in the NOC and accounted for 32% of the total holoplankton omnivore standing stock. In the NOC and IC, the carnivorous plankton accounted for 24 and 11% of the total plankton biomass, respectively. In the two sub-regions, 20 and 21% of the carnivores were meroplanktonic (primarily larvae of sprats and pilchards), while the holoplankton carnivores contributed 75 and 74% to the NOC and IC, respectively (Sagitta elegans, Pleurobrachia pileus). S. elegans dominated the holoplankton carnivore biomass for the majority of the year and accounted for 96% in the NOC and 60% in the IC. The integrated total particulate carbon over the 307 d period was 200 g C m^-3 (6 600 g C m^-2) in the NOC and 838 g C m^-3 (15 084 g C m^-2) in the IC. The annual primary production ranged from 164.9 g C m^-2 yr^-1 in the Outer Channel (North and South) to 6.8 g C m^-2 yr^-1 in the IC. The zooplankton biomass reached a maximum in July. The total particulate carbon (TPC) in July was 400 mg C m^-3 in the NOC of which ca. 78 mg C m^-3 were phytoplankton and ca. 21 mg C m^-3 were zooplankton; these values compare favourably with those found in the adjoining Celtic Sea. In the IC, the TPC was 2 800 mg C m^-3, of which ca. 107 mg C m^-3 were phytoplankton and 2.8 mg C m^-3 were zooplankton. From the low primary production estimates for the IC it can be concluded that the majority of the chlorophyll, like the TPC, was allochthonous in origin. Furthermore it is suggested that zooplankton plays a minor role in this estuarine ecosystem and is not the main consumer of the suspended particulate carbon; the benthic filter-feeding communities are presumed to fulfill this role in the Bristol Channel.     

Grazing by 35 to 202 μm micro-zooplankton in Long Island Sound

Micro-zooplankton abundance in Long Island Sound varied from 10³ to 10⁴ animals l^-1 at the station studied and consisted almost entirely of tintinnids. The micro-zooplankton were found to sometimes remove a significant portion of the chlorophyll a standing stock, with an upper limit of 41% of the standing stock being ingested per day. Observed ingestion rates ranged from 0.001 to 0.17 ng chlorophyll a removed animal^-1 h^-1 and from 0.06 to 87 cells removed animal^-1 h^-1, depending on season and type of cell being ingested. Filtering rates varied from 1.03 to 84.7 l animal^-1 h^-1. As a community, the micro-zooplankton exhibited the same order of magnitude ingestion and filtering rates as those noted for copepods.Contribution No. 259 of the Marine Sciences Center     

Primary production of sands in the lagoon of an atoll and the role of foraminiferan symbionts

Chlorophyll content and in situ oxygen production of sands were measured in the lagoon of Takapoto Atoll, Tuamotu Islands (French Polynesia). Stations were spaced from a depth of 17 m to the water limit on the beach. Photosynthetic pigments and net primary production for the top 3 cm of sediment ranged from 56 to 907 mg chlorophyll a m^-2 and from 115 to 354 mg O₂ m^-2 h^-1, respectively. Responsible organisms were mostly Foraminifera, among which Amphistegina lessoni, containing unicellular symbionts, dominated. The sands are thus significant contributors to the lagoon's primary production, while the role of phytoplankton is comparatively negligible.     

In situ net primary productivity and photosynthesis of Antarctic sea ice algal, phytoplankton and benthic algal communities

Primary production at Antarctic coastal sites is contributed from sea ice algae, phytoplankton and benthic algae. Oxygen microelectrodes were used to estimate sea ice and benthic primary production at several sites around Casey, a coastal area in eastern Antarctica. Maximum oxygen export from sea ice was 0.95 mmol O₂ m⁻² h⁻¹ (~11.7 mg C m⁻² h⁻¹) while from the sediment it was 6.08 mmol O₂ m⁻² h⁻¹ (~70.8 mg C m⁻² h⁻¹). When the ice was present O₂ export from the benthos was either low or negative. Sea ice algae assimilation rates were up to 3.77 mg C (mg Chl-a)⁻¹ h⁻¹ while those from the benthos were up to 1.53 mg C (mg Chl-a)⁻¹ h⁻¹. The contribution of the major components of primary productivity was assessed using fluorometric techniques. When the ice was present approximately 55–65% of total daily primary production occurred in the sea ice with the remainder unequally partitioned between the sediment and the water column. When the ice was absent, the benthos contributed nearly 90% of the primary production.     

Persistent blooms of surf diatoms along the Pacific coast,USA

Productivity was studied in two diatom species, Chaetoceros armatum T. West and Asterionella socialis Lewin and Norris, which form persistent dense blooms in the surf zone along the Pacific coast of Washington and Oregon, USA. Past observations have shown that surf-diatom standing stock usually declines in summer along with concentrations of nitrate and ammonium. Using the ¹⁴C method, photosynthetic rates in natural surf samples were measured monthly for one year (October 1981 through September 1982) at a study site on the Washington coast. Also measured were temperature, salinity, dissolved nutrients, particulate carbon and nitrogen (used as estimates of phytoplankton C and N), and chlorophyll a. Assimilation numbers (P _max) were higher in summer (5 to 8 g C g^-1 chl a h^-1) than in winter (3 to 4gC). Specific carbon incorporation rates (µ_max) showed no obvious seasonality, mostly falling within the range of 0.09 to 0.13 g C g^-1 C(POC) h^-1. The discrepancy between the seasonal trends for chlorophyll-specific and carbon-specific rates reflects a change in the carbon-to-chlorophyll ratio. Because of seasonal differences in daylength and light intensity, daily specific growth rates () are thought to be higher in summer than in winter. Neither ammonium enrichment assays nor particulate carbon-to-nitrogen ratios provided convincing evidence for nitrogen limitation during summer, and the observed changes in diatom abundance cannot be explained on this basis. Both the high diatom concentrations and their seasonal variations probably are due mainly to factors other than growth rates; two factors considered important are diatom flotation and seasonal changes in wind-driven water transport. C. armatum usually dominates the phytoplankton biomass in the surf zone, and evidence suggests that this species is strongly dominant in terms of primary production.Contribution No. 1391 of the School of Oceanography, University of Washington, Seattle, Washington, USA     

Strong variability in bacterioplankton abundance and production in central and western Bay of Bengal

With large influx of freshwater that decreases sea-surface salinities, weak wind forcing of <10 m s⁻¹ and almost always warm (>28°C) sea-surface temperature that stratifies and shallows the mixed layer leading to low or no nutrient injections into the surface, primary production in Bay of Bengal is reportedly low. As a consequence, the Bay of Bengal is considered as a region of low biological productivity. Along with many biological parameters, bacterioplankton abundance and production were measured in the Bay of Bengal during post monsoon (September–October 2002) along an open ocean transect, in the central Bay (CB, 88°E) and the other transect in the western Bay (WB). The latter representing the coastal influenced shelf/slope waters. Bacterioplankton abundances (<2 × 10⁹cells l⁻¹) were similar to those reported from the HNLC equatorial Pacific and the highly productive northern Arabian Sea. Yet, the thymidine uptake rates along CB (average of 1.46 pM h⁻¹) and WB (average of 1.40 pM h⁻¹) were less than those from the northwestern Indian Ocean. These abundances and uptake rates were higher than those in the oligotrophic northwestern Sargasso Sea (<7 × 10⁸ cells l⁻¹; av 1.0 pM h⁻¹). Concentrations of chlorophyll a (chl a), primary production rates and total organic carbon (TOC) were also measured for a comparison of heterotrophic and autotrophic production. In the WB, bacterioplankton carbon biomass equaled ∼ 95% of chl a carbon than just 31% in the CB. Average bacterial:primary production (BP:PP) ratios accounted for 29% in the CB and 31% in the WB. This is mainly due to lower primary productivity (PP) in the WB (281 mg C m⁻² d⁻¹) than in the CB (306 mg C m⁻² day⁻¹). This study indicates that bacteria–phytoplankton relationship differs in the open (CB) and coastal waters (WB). Higher abundance and contrastingly low bacterial production (BP) in WB may be because of the riverine bacteria, brought in through discharges, becoming dormant and unable to reproduce in salinities of 28 or more psu. Heterotrophic bacteria appear to utilize in situ DOC rather rapidly and their carbon demand is ∼50% of daily primary production. It is also apparent that allochthonous organic matter, in particular in the western Bay, is important for meeting their carbon demand.     

Primary productivity studies in the shelf waters off Alleppey,south-west India,during the post-monsoon, 1967

Primary productivity was measured by the radio-carbon method, its relation to the distribution of inorganic phosphate and dissolved oxygen off the south-west coast of India is discussed. The study was conducted during the post-monsson season which is associated with coastal upwelling. Productivity rates were generally high (807 mgC/m²/day), and so was the nutrient level in the euphotic zone. Inorganic phosphate was measured and taken as representative index of nutrients in general. Carbon assimilation rates were correlated with chlorophyll a, as well as with chlorophylls a, b plus c. Plant carotenoids were also measured but their role is not clear. Standing crop estimations failed to show any good agreement with carbon assimilation. Dark bottle correction at lower levels of the euphotic zone in coastal waters is discussed. The various results are interpreted from the point of view of light ecology. Fluctuations in productivity are mainly due to variations in incident solar radiation.     

The common jellyfish Aurelia aurita: standing stock,excretion and nutrient regeneration in the Kiel Bight,Western Baltic

The population dynamics, ammonia and inorganic phosphate excretion, and nutrient regeneration of the common jellyfish Aurelia aurita was investigated from 1982 to 1984 in the Kiel Bight, western Baltic Sea. During summer 1982, medusae abundance ranged between 14 and 23 individuals 100 m^-3, biomass was estimated at about 5 g C 100 m^-3 and the mean final diameter of individuals was 22 cm. Abundance, based on numbers, in 1983 and 1984 was an order of magnitude lower; biomass was less than 2 g C 100 m^-3 and jellyfish grew to 30 cm. During the summers of 1983 and 1984, A. aurita biomass constituted roughly 40% of that of the total zooplankton>200 m. In 1982, for which zooplankton data were lacking, it was assumed that medusae biomass was greater than that of all other zooplankton groups. Total ammonia excretion ranged between 6.5 and 36 mol h^-1 individual^-1, whereas inorganic phosphate release was 1.4 to 5.7 mol h^-1 individual^-1. Allometric equations were calculated and exponents of 0.93 for NH₄–N release and 0.87 for PO₄–P excretion were determined. Nitrogen and phosphorus turnover rates were 5.4 and 14.6% d^-1, respectively. In 1982, the medusae population released 1 100 mol NH₄–N m^-2 d^-1, about 11% of the nitrogen requirements of the phytoplankton. The inorganic phosphate excretion (150 mol m^-2 d^-1) sustained 23% of the nutrient demands of the primary producers. In the other two years the nutrient cycling of the medusae was much less important, and satisfied only 3 to 6% of the nutrient demands. It is suggested that in some years A. aurita is the second most important source of regenerated nutrients in Kiel Bight, next to sediment.     

Seasonal study of phytoplankton pigments and species at a coastal station off Sydney: Importance of diatoms and the nanoplankton

Phytoplankton pigments and species were studied at a coastal station off Sydney (New South Wales, Australia) over one annual cycle. Sudden increases in chlorophyll a (up to 280 mg m^-2), due to short-lived diatom blooms, were found in May, July, September, January and February. These were superimposed upon background levels of chlorophyll a (20 to 50 mg m^-2), due mostly to nanoplankton flagellates, which occurred throughout the year. The nanoplankton (<15 m) accounted for 50 to 80% of the total phytoplankton chlorophyll, except when the diatom peaks occurred (10 to 20%). The annual cycle of populations of 16 dominant species-groups was followed. Possible explanations as to alternation of diatom-dominated and nanoplankton-dominated floras are discussed. Thin-layer chromatography of phytoplankton pigments was used to determine the distribution of algal types, grazing activity, and phytoplankton senescence in the water column. Chlorophyll c and fucoxanthin (diatoms and coccolithophorids) and chlorophyll b (green flagellates) were the major accessory pigments throughout the year, with peridinin (photosynthetic dinoflagellates) being less important. Grazing activity by salps and copepods was apparent from the abundance of the chlorophyll degradation products pheophytin a (20 to 45% of the total chlorophyll a) and pheophorbide a (10 to 30%). Chlorophyllide a (20 to 45%) was associated with blooms of Skeletonema costatum and Chaetoceros spp. Small amounts of other unidentified chlorophyll a derivatives (5 to 20%) were frequently observed.     

Primary production and environmental factors in an oligotrophic biome in the Aegean Sea

The rate of the primary production of the phytoplankton community in the Petalion Gulf, Aegean Sea, was studied from January 1970 to May 1971, at a station situated at approximately Latitude 37°54N; Longitude 24°11E. A variety of physical and chemical parameters such as chlorophyll, primary nutrients (N,P,Si), temperature, salinity, oxygen and light penetration were also studied simultaneously. The rate of the gross primary production varied from 40 to 200 mg C m^-2 day^-1, with a mean value of 90 mg C m^-2 day^-1. The annual gross primary production was calculated to be 33 g C m^-2, which is the minimum known value in the Aegean and Mediterranean Seas. Maximum production was found at the depth of 20 m on the average, mainly due to high light intensities. Petalion Gulf supports a small photosynthetic biomass, as indicated by the low seasonal values of chlorophyll a (0.01 to 0.18 mg m^-2), the highest values being found in the summer. The low production rate noted may have been due to the low nutrient concentrations found: N, 0.04 to 0.32 g-at/1; P, 0.00 to 0.15 g-at/1; Si, 0.45 to 2.25 g-at/1. It is suggested that inorganic phosphorus and nitrogen may alternate in limiting primary production rates in these oligotrophic waters. The temperate waters of the Petalion Gulf are stratified in summer (15.5° to 24.7°C) and well-mixed in winter (12.9° to 15.0°C); they are oxygen-saturated throughout the year, and of high transparency, with 86 m depth for the euphotic zone on the average yearly. The Petalion Gulf is therefore characterized as a typical oligotrophic biome in the Aegean and Eastern Mediterranean Seas.     

A comparative seasonal study of two populations of Hypnea musciformis from the East and West Coasts of Florida,USA I. Growth and chemistry

Dry weight levels of the red alga Hypnea musciformis (Wulfen) Lamouroux from Atlantic and Gulf of Mexico coastal sites in florida, USA were lowest in the late winter and early spring, increasing through the summer and highest in the fall. There was a two-month lag in the Gulf coast population's dry weight pattern, indicating differing growth patterns. Chlorophyll a, phycoerythrin and phycoerythrin/chlorophyll a ratios were highest in the winter and lowest in the summer for both populations. Total pigment levels for H. musciformis from the Atlantic coast site were significantly greater than those of the Gulf coast. Protein and carbohydrate percentages were inversely related in both populations, with carbohydrate levels highest in summer and protein levels highest in winter. The Gulf coast population contained significantly more protein than the Atlantic coast plants. Carrageenan levels were highest in spring and lowest in fall, the Atlantic coast population generally had higher levels than the Gulf coast population. The differences in seasonal patterns and levels of the chemical constituents were reflected by distinct morphological characteristics for each population. The Atlantic coast population was larger, darker, more coarse in texture and possessed more crozier branch tips than the Gulf coast plants. These distinctions represent acclimitization responses that relate to habitat differences.     

Primary productivity and the flux of dissolved organic matter in several marine environments

Primary productivity and the flux of DO¹⁴C, dissolved saccharides (DSAC) and dissolved free primary amines (DFPA) were followed in the Sargasso Sea, Caribbean and upwelling waters of Peru. Average carbon fixation rates were 42.8, 292.8 and 4791.6 mg C m^-2 d^-1, respectively, with nocturnal respiration rates ranging from 9.8–16.3% of gross photosynthesis for the 3 areas. The release of DO¹⁴C, as a percentage of the total carbon fixed in photosynthesis, was non-detectable in the Sargasso Sea, and 3.2 and 4.4% for the Caribbean and Peruvian phytoplankton communities. Few significant changes in DSAC concentrations were recorded over a 36-h incubation period in the Sargasso Sea and Caribbean stations, whereas light-dependent accumulations of DSAC and DFPA were noted in Peruvian stations which were strongly correlated with total phytoplankton productivity. In the Peruvian stations, the average accumulation rate was 234 mg DSAC-C m^-2h^-1 while the average rate of nocturnal decomposition was 141 mg DSAC-C m^-2h^-1; diurnal and nocturnal rates of DFPA accumulation and decomposition were similar (2 mg DFPA-C m^-2h^-1). These data were used to calculate bacterial production in the upwelling waters of Peru. A general discussion of ¹⁴C-technique and routine analytical techniques for DSAC analysis is presented, as DSAC flux exceeded DO¹⁴C flux by 17-fold in coastal Peruvian stations.