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1.
C. D. Dubischar E. A. Pakhomov L. von Harbou B. P. V. Hunt U. V. Bathmann 《Marine Biology》2012,159(1):15-24
Two species of salps, Salpa thompsoni and Ihlea racovitzai, were sampled during three cruises to the Lazarev Sea, Southern Ocean, in summer (December–January) 2005/2006, Autumn (April–May)
2004 and Winter (July–August) 2006. Dry weight, carbon, nitrogen, protein, lipid and carbohydrate contents were measured to
characterize the potential value of salps as a food source for predators in the Antarctic ecosystem. Biochemical composition
measurements showed that despite having a high percentage of water (~94% of wet weight), both species had relatively high
carbon and protein contents in their remaining dry weight (DW). In particular I. racovitzai showed high carbon (up to 22% of DW) and protein (up to 32% of DW) values during all seasons sampled, compared to lower values
for S. thompsoni (carbon content only about 15% of the DW, protein content about 10% of the DW). At the same time, carbohydrates (CH) and
lipids (Lip) only accounted for a small portion of salp DW in both species (1.4% CH and 3.6% Lip for I. racovitzai; 2.1% CH and 2.9% Lip for S. thompsoni). There was little variability in the biochemical composition of either salp species between the seasons sampled. Both biochemical
composition and life cycle characteristics suggest that Antarctic salps, especially I. racovitzai, may be important prey items for both cold and warm-blooded predators in an environment where food is often very scarce. 相似文献
2.
Feeding association of the copepod Rhincalanus gigas with the tunicate salp Salpa thompsoni in the southern ocean 总被引:1,自引:1,他引:1
During a repeat grid survey and drogue study carried out in the Lazarev Sea in the austral summer of 1994 to 1995, a sudden
collapse of a rich population of the tunicate Salpa thompsoni was observed at the onset of a phytoplankton bloom. This may have been related to the inability of salps to regulate their
filtration rate and avoid clogging of their filtering apparatus at particle concentrations ≥1 mg (chlorophyll a) m−3. It was at this stage that large numbers of salp individuals had their branchial cavities invaded by the copepod Rhincalanus gigas. Incubations, to compare the feeding rates of R.␣gigas in the presence and absence of salps, showed that copepods are able to utilize the high concentrations of microplankton accumulated
in the food strand of the salp, thus enhancing their grazing efficiency. This is likely to represent a typical form of opportunistic
parasitism. However, the timing of the invasion, and the observation that most salps could survive prolonged exposure to R. gigas invasion, suggest that the association may also constitute a novel type of symbiosis. S.␣thompsoni could potentially benefit from R. gigas cleaning its filtering apparatus when clogging due to high particle concentrations occurs.
Received: 15 July 1996 / Accepted: 20 July 1996 相似文献
3.
Contribution of salps to carbon flux of marginal ice zone of the Lazarev Sea, southern ocean 总被引:3,自引:0,他引:3
In order to estimate the in situ grazing rates of Salpa thompsoni and their implications for the development of phytoplankton blooms and for the sequestration of biogenic carbon in the high
Antarctic, a repeat-grid survey and drogue study were carried out in the Lazarev Sea during austral summer of 1994/1995 (December/January).
Exceptionally high grazing rates were measured for S. thompsoni at the onset of a phytoplankton bloom (0.2 to 0.8 μg chlorophyll a l−1) in December 1994, with up to ≃160 μg of plant pigments consumed by an individual salp of 7 to 10 cm length per day. Dense
salp swarms extended throughout the marginal ice zone, consuming up to 108% of daily phytoplankton production and 21% of the
total chlorophyll a stock. Due to the much faster sinking rates and higher carbon content of salp faecal pellets, the efficiency of downward
carbon flux through salps is much higher than through the other major grazers, krill and copepods. S. thompsoni can thus export large amounts of biogenic carbon from the euphotic zone to the deep ocean. With the observed ingestion rates
during December 1994, this flux could have attained levels of up to 88 mg C m−2 d−1, accounting for the bulk of the vertical transport of carbon in the Lazarev Sea. However, in January 1995, when phytoplankton
concentrations exceeded a threshold level of 1.0 to 1.5 μg chlorophyll a l−1, salps experienced a drastic reduction in their feeding efficiency, possibly as a result of clogging of their filtering apparatus.
This triggered a dramatic reversal in the relationship, during which a dense phytoplankton bloom developed in conjunction
with the collapse of the salp population. Increases in the biomass and geographic range of the tunicate S. thompsoni have occurred in several areas of the southern ocean, often in parallel with a rise in sea-surface temperature during sub-decadal
periods of warming anomalies.
Received: 10 August 1997 / Accepted: 21 October 1997 相似文献
4.
Measurements of the defecation rate of Salpa thompsoni were made at several stations during two cruises west of the Antarctic Peninsula in 2004 and 2006. Rates were quantified
in terms of number of pellets, pigment, carbon and nitrogen for a wide size range of both aggregate and solitary salps. Measured
defecation rates were constant over several hours when salps were held at near-surface conditions from which they had been
collected. The defecation rate per salp increased with both salp size and the ambient level of particulate organic matter
(POM) in the upper water column. The weight-specific defecation rate ranged between 0.5 and 6% day−1 of salp body carbon, depending on the concentration of available particulate matter in the water. Carbon defecation rates
were applied to biomass estimates of S. thompsoni to calculate daily carbon defecation rates for the populations sampled during the two cruises. Dense salp populations of
over 400 mg C m−2 were calculated to produce about 20 mg C m−2 day−1, comparable to other major sources of vertical flux of organic material in the Southern Ocean. Measured sinking rates for
salp fecal pellets indicated that the majority of this organic material could reach deep sediments within a few days, providing
a fast and direct pathway for carbon to the deep ocean. 相似文献
5.
Annual cycles of phytoplankton community-structure and bloom dynamics in the Neuse River Estuary, North Carolina 总被引:6,自引:0,他引:6
The spatiotemporal distributions of major phytoplankton taxa were quantified to estimate the relative contribution of different
microalgal groups to biomass and bloom dynamics in the eutrophic Neuse River Estuary, North Carolina, USA. Biweekly water
samples and ambient physical and chemical data were examined at sites along a salinity gradient from January 1994 through
December 1996. Chemosystematic photopigments (chlorophylls and carotenoids) were identified and quantified using high-performance
liquid chromatography (HPLC). A recently-developed factor-analysis procedure (CHEMTAX) was used to partition the algal group-specific
chlorophyll a (chl a) concentrations based on photopigment concentrations. Results were spatially and temporally integrated to determine the ecosystem-level
dynamics of phytoplankton community-constituents. Seasonal patterns of phytoplankton community-composition changes were observed
over the 3 yr. Dinoflagellates reached maximum abundance in the late winter to early spring (January to March), followed by
a spring diatom bloom (May to July). Cyanobacteria were more prevalent during summer months and made a large contribution
to phytoplankton biomass, possibly in response to nutrient-enriched freshwater discharge. Cryptomonad blooms were not associated
with a particular season, and varied from year to year. Chlorophyte abundance was low, but occasional blooms occurred during
spring and summer. Over the 3 yr period, the total contribution of each algal group, in terms of chl a, was evenly balanced, with each contributing nearly 20% of the total chl a. Cryptomonad, chlorophyte, and cyanobacterial dynamics did not exhibit regular seasonal bloom patterns. High dissolved inorganic-nitrogen
loading during the summer months promoted major blooms of cryptomonads, chlorophytes, and cyanobacteria.
Received: 12 September 1997 / Accepted: 12 December 1997 相似文献
6.
E. A. Pakhomov C. D. Dubischar V. Strass M. Brichta U. V. Bathmann 《Marine Biology》2006,149(3):609-623
Distribution, density, and feeding dynamics of the pelagic tunicate Salpa thompsoni have been investigated during the expedition ANTARKTIS XVIII/5b to the Eastern Bellingshausen Sea on board RV Polarstern in April 2001. This expedition was the German contribution to the field campaign of the Southern Ocean Global Ocean Ecosystems Dynamics Study (SO-GLOBEC). Salps were found at 31% of all RMT-8 and Bongo stations. Their densities in the RMT-8 samples were low and did not exceed 4.8 ind m−2 and 7.4 mg C m−2. However, maximum salp densities sampled with the Bongo net reached 56 ind m−2 and 341 mg C m−2. A bimodal salp length frequency distribution was recorded over the shelf, and suggested two recent budding events. This was also confirmed by the developmental stage composition of solitary forms. Ingestion rates of aggregate forms increased from 2.8 to 13.9 μg (pig) ind−1 day−1 or from 0.25 to 2.38 mg C ind−1 day−1 in salps from 10 to 40 mm oral-atrial length, accounting for 25–75% of body carbon per day. Faecal pellet production rates were on average 0.08 pellet ind−1 h−1 with a pronounced diel pattern. Daily individual egestion rates in 13 and 30 mm aggregates ranged from 0.6 to 4.8 μg (pig) day−1 or from 164 to 239 μg C day−1. Assimilation efficiency ranged from 73 to 90% and from 65 to 76% in 13 and 30 mm aggregates, respectively. S. thompsoni exhibited similar ingestion and egestion rates previously estimated for low Antarctic (~50°S) habitats. It has been suggested that the salp population was able to develop in the Eastern Bellingshausen Sea due to an intrusion into the area of the warm Upper Circumpolar Deep Water 相似文献
7.
Two vegetative clones (designated 11/85 and 7/86 in accordance with month/year of collection) of the chlorophyte macroalga Ulva rotundata were collected in the vicinity of Beaufort, North Carolina, USA. Each was grown in an outdoor continuous-flow system in summer (>-20°C) of 1986 and late winter (10° to 17°C) of 1987 in graded scalar quantum irradiances ranging from 9 to 100% of full sunlight, with and without NH
4
+
enrichment. The pigment content of plants from each irradiance was determined following 4 to 8 d sunny weather. Chlorophyll (chl) and carotenoid content were inverse curvilinear functions of irradiance. The chl a:b and carotenoid: chl ratios were positively related to irradiance. The close nonlinear relationship between chl (a+b) and the chl a:b ratio was independent of clone, temperature or NH
4
+
-enrichment. Chl (a+b) content was linearly correlated with light-regulated growth rate in the summer, but showed a marked hysteresis in the relationship in winter due to photoinhibition. The photon growth yield (PGY, i.e., the biomass yield per unit absorbed light) was maximal for plants grown at slightly subsaturating irradiances, and dropped off sharply at lower irradiances. At higher irradiances, PGY declined gradually in summer and markedly in winter. Light absorption exceeded growth needs at full sunlight, suggesting that U. rotundata was incapable of further reducing its pigment content when growth rate was light-saturated. This, along with the linear chlgrowth relationship, is consistent with photosynthetic feedback regulation of chl content. Regardless of the mechanism, chl regulation may operate within the constraints of a resource tradeoff between light harvesting and carboxylation capacities, such that pigmentation must be optimized rather than maximized. 相似文献
8.
The Gulf of Aqaba exhibits a strong seasonality due to convective mixing during winter and stratification during summer. The present study provides a detailed appraisal of summer and winter sea-water characteristics at the northern coast of the Gulf of Aqaba, that is witnessing rapid development and increasing changes in its geomorphological characteristics. Sea-water temperature, salinity, nutrients, and chlorophyll a concentrations were measured biweekly at five coastal and four cross-sectional stations during the periods February to April and July to September 2004. Meteorological conditions were continuously recorded at the Marine Science Station. The coastal study sites included four open coastal stations and a marina with one-way exchange with the open water. The effect of convective mixing was clearly apparent on the sea-water characteristics. Natural seasonal characteristics of higher nutrients and chlorophyll a concentrations were recorded during winter at most of the open coastal stations. In the cross-sectional stations, the concentrations of nutrients and chlorophyll a were not different between the surface and the bottom during winter, but the bottom waters had generally higher concentrations during summer. Some deviations from the natural seasonal cycle were recorded at the marina and other coastal stations. Here, higher nutrient and chlorophyll a concentrations were recorded in summer than in winter. These deviations that are most likely due to anthropogenic effects are discussed. 相似文献
9.
Detailed determination of Salpa thompsoni elemental composition has been carried out on specimens collected in the Eastern Bellingshausen Sea and at the northern edge of the Weddell Gyre during austral autumn (April and May) of 1996 and 2001. More than 170 Antarctic tunicates S. thompsoni were analysed to determine wet weight (WW), dry weight (DW), ash-free dry weight (AFDW) and elemental composition (C, N content, proteins, carbohydrates and lipids) of different sizes and stages. Dry weight comprised 6.4% (aggregate form) to 7.7% (solitary form) of the WW. AFDW amounted to ~44% of the DW. Carbon and nitrogen contents (Carbon: 17–22%, Nitrogen: 3–5% of the DW) of both aggregate and solitary forms were found to be high relative to data reported in the literature. Although some unidentified organic compounds are not included in our carbon budget, the findings of this study show higher than previously reported nutritional values of S. thompsoni. In spite of this, a shift from a krill-dominated towards a salp-dominated ecosystem would have dramatic consequences for organisms at higher trophic levels. 相似文献
10.
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 (µmax) 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 相似文献
11.
Nutrients were added separately and combined to an initial concentration of 10 μM (ammonium) and/or 2 μM (phosphate) in a series of experiments carried out with the giant clam Tridacna maxima at 12 microatolls in One Tree Island lagoon, Great Barrier Reef, Australia (ENCORE Project). These nutrient concentrations
remained for 2 to 3 h before returning to natural levels. The additions were made every low tide (twice per day) over 13 and
12 mo periods for the first and second phase of the experiment, respectively. The nutrients did not change the wet tissue
weight of the clams, host C:N ratio, protein content of the mantle, calcification rates or growth rates. However, ammonium
(N) enrichment alone significantly increased the total population density of the algal symbiont (Symbiodinium sp.: C = 3.6 · 108 cell clam−1, N = 6.6 · 108 cell clam−1, P = 5.7 · 108 cell clam−1, N + P = 5.7 · 108 cell clam−1; and C = 4.1 · 108 cell clam−1, N = 5.1 · 108 cell clam−1, P = 4.7 · 108 cell clam−1, N + P = 4.5 · 108 cell clam−1, at the end of the first and second phases of the experiment, respectively), although no differences in the mitotic index
of these populations were detected. The total chlorophyll a (chl a) content per clam but not chlorophyll a per cell also increased with ammonium addition (C = 7.0 mg chl a clam−1, N = 13.1 mg chl a clam−1, P = 12.9 mg chl a clam−1, N + P = 11.8 mg chl a clam−1; and C = 8.8 mg chl a clam−1, N = 12.8 mg chl a clam−1; P = 11.2 mg chl a clam−1, N + P = 11.3 mg chl a clam−1, at the end of the first and second phases of the experiment, respectively). The response of clams to nutrient enrichment
was quantitatively small, but indicated that small changes in inorganic nutrient levels affect the clam–zooxanthellae association.
Received: 2 June 1997 / Accepted: 9 June 1997 相似文献
12.
During two expeditions of the R.V. Polarstern to the Arctic Ocean, pack ice and under-ice water samples were collected during two different seasons: late summer (September 2002) and late winter (March/April 2003). Physical and biological properties of the ice were investigated to explain seasonal differences in species composition, abundance and distribution patterns of sympagic meiofauna (in this case: heterotrophs >20 µm). In winter, the ice near the surface was characterized by extreme physical conditions (minimum ice temperature: –22°C, maximum brine salinity: 223, brine volume: 5%) and more moderate conditions in summer (minimum ice temperature: –5.6°C, maximum brine salinity: 94, most brine volumes: 5%). Conditions in the lowermost part of the ice did not differ to a high degree between summer and winter. Chlorophyll a concentrations (chl a) showed significant differences between summer and winter: during winter, concentrations were mostly <1.0 µg chl a l–1, while chl a concentrations of up to 67.4 µmol l–1 were measured during summer. The median of depth-integrated chl a concentration in summer was significantly higher than in winter. Integrated abundances of sympagic meiofauna were within the same range for both seasons and varied between 0.6 and 34.1×103 organisms m–2 in summer and between 3.7 and 24.8×103 organisms m–2 in winter. With regard to species composition, a comparison between the two seasons showed distinct differences: while copepods (42.7%) and rotifers (33.4%) were the most abundant sea-ice meiofaunal taxa during summer, copepod nauplii dominated the community, comprising 92.9% of the fauna, in winter. Low species abundances were found in the under-ice water, indicating that overwintering of the other sympagic organisms did not take place there, either. Therefore, their survival strategy over the polar winter remains unclear.Communicated by O. Kinne, Oldendorf/Luhe 相似文献
13.
Vincent Ouisse Pascal Riera Aline Migné Cédric Leroux Dominique Davoult 《Marine Biology》2012,159(1):165-175
The food web of two intertidal seagrass (Zostera marina and Zostera noltii) beds that may be influenced by the seasonal variation in food source abundance was studied in winter and in summer with
δ13C and δ15N analysis. In spite of high relative variation of abundance of main primary producers at the two sites, the food web did
not vary between winter and summer. The δ13C range of primary producers was wide. Zostera leaves, the most 13C-enriched source, were not consumed directly by grazers. Deposit and filter feeders have a similar δ13C and could use a mix of suspended and sedimented organic particulate matter, largely composed of detritus from macroalgae
to seagrass. This trophic pathway allows the local incorporation of the high biomass produced by seagrasses. The wide δ15N range of predators was linked either to a large variety from omnivore to carnivore predators or to the also wide ranges
of δ15N of primary consumers. 相似文献
14.
The mud crab Scylla serrata is an important commercial crustacean being widely distributed along the southeastern coast of China. This crab and particularly
its gills are subjected to seasonal fluctuations of environmental factors due to direct exposure to seawater. The investigation
of seasonal variations of ATPase and antioxidant defenses in gills could be helpful for the understanding of physiological
regulation mechanism of seasonal adaptations. In this study, mud crabs were collected from the subtropical waters near Xiamen
island, Southeast China (24°26′46′′N, 118°04′04′′E), in August and November, 2002, and February and May, 2003, respectively,
being considered as specimens from summer, autumn, winter and spring, respectively. Only healthy intermoult male crabs without
carapace or appendage damage were used, having a carapace width of 7.05 ± 0.52 cm and a wet weight of 130 ± 20 g. The activities
of four ATPases and three antioxidation enzymes (superoxide dismutase, catalase, glutathione peroxidase) and the content of
malondialdehyde in gills were measured. The results showed that the activities of Na+, K+-ATPase, Mg2+-ATPase, Ca2+-ATPase and Ca2+, Mg2+-ATPase reached maximum levels similarly in summer and decreased in winter. The activities of superoxide dismutase and catalase
were higher in summer and lower in winter, with a significant decrease in winter compared to the other seasons (p < 0.01). Glutathione peroxidase activity was higher in summer, and lower in autumn, being significantly higher in summer or
winter than in spring or autumn (p < 0.01). Malondialdehyde content was higher in summer and lower in spring with significant differences among the different
seasons (p < 0.01). In summary, the obvious seasonal activity variations of four ATPases and antioxidant enzymes and the content of malondialdehyde
reflect a seasonal regulation of the physiological metabolising enzyme and the antioxidant capacity to cope with seasonal
alterations of environment factors such as fluctuating salinities and temperatures. 相似文献
15.
In order to understand the relationships between the dynamics of phytoplankton populations in the surface microlayer (MIL)
and in the water column below (SSW), this study used high-performance liquid chromatography-derived pigment markers in samples
from a coastal lagoon of Baja California (Estero de Punta Banda, EPB) under summer (October 2003) and winter (December 2003)
conditions. Photosynthetic pigment signatures of phytoplankton at the air–sea interface (phytoneuston) and subsurface measurements
were related to bottom-up (temperature, salinity, nutrient concentrations) and top-down factors (zooplankton abundance). Slicks
and scum layers were observed in the inner part of the lagoon and coincided with greater stratification of layers just below
the sea surface and lower wind intensities. In general, spatial variability in pigment markers and ancillary data was very
high and resulted in non-significant differences between MIL and subsurface samples when different regions of EPB or sampling
dates were compared. However, different patterns were found between pigments and environmental factors of MIL and SSW samples
when the relative numbers of stations with positive and negative differences (ΔX = X
MIL−X
SSW) were computed. For each survey, pigment markers of phytoneuston and phytoplankton samples were not necessarily correlated.
Further analysis revealed that those markers (19′-butanoyloxyfucoxanthin, prasinoxanthin, divinil-chlorophyll a) corresponded to picophytoplankton groups (haptophyte, prasinophyte, and prochlorophyte). On both dates, the MIL was enriched
in 19′-hexanoyloxyfucoxanthin (a marker for a type 4 haptophyte) and fucoxanthin (marker for bacillariophytes, haptophytes,
and crysophytes) and depleted in peridinin (marker for dinophytes). Different zooplankton grazers accumulated in the MIL (loricate
tintinnids) and in SSW (copepod nauplii). 相似文献
16.
The Belizean reef coral Agaricia tenuifolia Dana forms aggregations in which rows of thin, upright blades line up behind each other. On average, the spacing between
blades increases with depth and hence with decreasing ambient irradiance. We designed and built a small, inexpensive light
meter and used it to quantify the effect of branch spacing on light levels within colonies at varying distances from branch
tips. Concurrently, we measured photosynthetic pigment concentrations and population densities of symbiotic dinoflagellates
(zooxanthellae) extracted from coral branches of colonies with tight (≤3 cm) vs wide (≥6 cm) branch spacing, collected at
15 to 17 m and from colonies with tight branch spacing collected at 1 to 2 m. Light levels decreased significantly with tighter
branch spacing and with distance from the branch tips. Total cellular pigment concentrations (chlorophylls a, c
2
and peridinin) as well as chlorophyll a:c
2
and chlorophyll a: peridinin ratios all increased significantly with distance from the branch tip, indicating very localized differences in
photoacclimation within individual branches. Zooxanthellae from colonies with widely-spaced branches displayed significantly
lower chlorophyll a:c
2
and chlorophyll a:peridinin ratios, and were present at significantly higher population densities than those from colonies with tightly-spaced
branches collected at the same depth (15 m). Tightly-spaced colonies collected from shallow environments (1 to 2 m) displayed
pigment ratios similar to those from widely-spaced colonies from deeper water (15 m), but maintained zooxanthellae populations
at levels similar to those in tightly-branched colonies from deeper water. Thus, variation in colony morphology (branch spacing
and distance from branch tip) can affect symbiont physiology in a manner comparable to an increase of over 15 m of water depth.
These results show that a host's morphology can strongly determine the microhabitat of its symbionts over very small spatial
scales, and that zooxanthellae can in turn display steep gradients in concordance with these altered physical conditions.
Received: 12 June 1997 / Accepted: 24 June 1997 相似文献
17.
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. 相似文献
18.
B. E. Lapointe 《Marine Biology》1987,93(4):561-568
The relative effects of NH
4
+
(N) and PO
4
3-
(P) on growth rate, photosynthetic capacity (Pmax), and levels of chemical constituents of the red macroalga Gracilaria tikvahiae McLachlan were assayed during winter and summer, 1983 in inshore waters of the Florida Keys by using in-situ cage cultures. During winter, both N and P enrichment enhanced growth over that of ambient seawater; however, P rather than N accounted for more (60%) of the increased winter growth. During summer, P, but not N, enhanced growth over ambient seawater and accounted for 80% of increased growth. Similarly, Pmax was enhanced by both P and N during winter (but mostly by P) and only by P during summer. Elevated C:P, C:N and N:P ratios of G. tikvahiae tissue during winter, but only C:P and N:P ratios during summer, support the pattern of winter N and P limitation and summer P-limitation. This seasonal pattern of N vs P limited growth of G. tikvahiae appears to be a response to seasonally variable dissolved inorganic N (twofold greater concentrations of NH
4
+
and NO
3
-
during summer compared to winter) and constantly low to undetectable concentrations of PO
4
3-
. Mean C:P and N:P ratios of G. tikvahiae tissue during the study were 1 818 and 124, respectively, values among the highest reported for macroalgae. 相似文献
19.
Metallothionein-like proteins (MTLs) have been measured by differential pulse polarography every two months during a period
of two and half years in the marine bivalve Macoma balthica from two locations of the Western Scheldt Estuary. The MTL concentrations (0.85 to 7.81 mg g−1 dry wt) are comparable to most values found for other marine invertebrates. These concentrations vary significantly with
the seasons (higher in winter, lower in summer), which is mainly due to body weight fluctuations. Strong correlations exist
between MTL and metal levels. Upon short-term exposure to a mixture of Cd, Cu and Zn, there are on average significant MTL
increases, but important seasonal variations have been observed: in winter, the clams are more sensitive to metals, uptake
more Cd and Cu and induce more MTL than during the warmer months.
Received: 16 May 1997 / Accepted: 6 June 1997 相似文献
20.
Phytoplankton community structure and primary production in small intertidal estuarine-bay ecosystem (eastern English Channel,France) 总被引:1,自引:0,他引:1
From May 2002 to October 2003, a fortnightly sampling programme was conducted in a restricted macrotidal ecosystem in the
English Channel, the Baie des Veys (France). Three sets of data were obtained: (1) physico-chemical parameters, (2) phytoplankton community structure illustrated
by species composition, biovolume and diversity, and (3) primary production and photosynthetic parameters via P versus E curves. The aim of this study was to investigate the temporal variations of primary production and photosynthetic parameters
in this bay and to highlight the potential links with phytoplankton community structure. The highest level of daily depth-integrated
primary production Pz (0.02–1.43 g C m−2 d−1) and the highest maximum photosynthetic rate P
B
max (0.39–8.48 mg C mg chl a
−1 h−1) and maximum light utilization coefficient αB [0.002–0.119 mg C mg chl a
−1 h−1 (μmol photons m−2 s−1)] were measured from July to September. Species succession was determined based on biomass data obtained from cell density
and biovolume measurements. The bay was dominated by 11 diatoms throughout the year. However, a Phaeocystis globosa bloom (up to 25 mg chl a m−3, 2.5 × 106 cells l−1) was observed each year during the spring diatom bloom, but timing and intensity varied interannually. Annual variation of
primary production was due to nutrient limitation, light climate and water temperature. The seasonal pattern of microalgal
succession, with regular changes in composition, biovolume and diversity, influenced the physico-chemical and biological characteristics
of the environment (especially nutrient stocks in the bay) and thus primary production. Consequently, investigation of phytoplankton
community structure is important for developing the understanding of ecosystem functioning, as it plays a major role in the
dynamics of primary production. 相似文献