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  • 1
    Online Resource
    Online Resource
    Temporarily Open/Closed Estuaries in South Africa. (2010)
    Hauppauge :Nova Science Publishers, Incorporated,
    Details
    Keywords: Estuaries--South Africa. ; Electronic books.
    Type of Medium: Online Resource
    Pages: 1 online resource (158 pages)
    Edition: 1st ed.
    ISBN: 9781616688257
    Series Statement: Environmental Science, Engineering and Technology
    URL: https://ebookcentral.proquest.com/lib/geomar/detail.action?docID=4689708
    DDC: 551.46180967999999
    Language: English
    Note: Intro -- TEMPORARILY OPEN/CLOSED ESTUARIES IN SOUTH AFRICA -- TEMPORARILY OPEN/CLOSED ESTUARIES IN SOUTH AFRICA -- LIBRARY OF CONGRESS CATALOGING-IN-PUBLICATION DATA -- CONTENTS -- PREFACE -- Chapter 1: INTRODUCTION -- Chapter 2: 2. HYDRODYNAMICS -- 2.1 CATCHMENT PROCESSES -- 2.1.1 Climactic Factors -- 2.1.2.Catchment Characteristics and Their Effects on Flows -- 2.1.3.Sediment Yields -- 2.1.4.Anthropogenic Changes -- 2.2. COASTAL PROCESSES -- 2.2.1. Wave Climate -- 2.2.2. Tides -- 2.2.3. Near-Shore Currents -- 2.2.4. Beaches and the Littoral Zone -- 2.3. ESTUARINE PROCESSES -- 2.3.1. Physical Characteristics that Affect Hydrodynamic Functioning -- 2.3.2. Water, Salinity and Nutrient Budgets -- 2.3.3. Mouth Dynamics -- 2.3.4. Tidal Exchange Flows -- 2.3.5. Wind-Driven Waves, Flows and Mixing -- 2.3.6. Sedimentation Patterns -- Chapter 3: 3. PHYSICO-CHEMICAL ENVIRONMENT -- 3.1. TEMPERATURE -- 3.2. SALINITY -- 3.3. IRRADIANCE -- 3.4. DISSOLVED OXYGEN -- 3.5. INORGANIC NUTRIENTS -- Chapter 4: 4. PRIMARY PRODUCERS -- 4.1. PHYTOPLANKTON -- 4.2.MICROPHYTOBENTHOS -- 4.3.MACROPHYTES -- Chapter 5: 5. CONSUMERS & -- TOP PREDATORS -- 5.1.MICROBIAL LOOP -- 5.2. ZOOPLANKTON -- 5.3.MEIOFAUNA -- 5.4.MACROBENTHOS -- 5.5. FISH -- 5.6. BIRDS -- Chapter 6: 6. THE FUTURE OF TOCES AND ROLE OF MANAGEMENT -- 6.1. CATCHMENT AND FLOW MANAGEMENT -- 6.2. ARTIFICIAL BREACHING -- 6.3. FLOOD PLAIN ENCROACHMENT -- 6.4. SAND MINING OPERATIONS -- 6.5. EXPLOITATION OF BIORESOURCES ANDRECREATIONAL ACTIVITIES -- 6.6. CULTURAL EUTROPHICATION -- 6.7. IMPACTS OF SEA-LEVEL RISEAND CLIMATE CHANGE -- 6.8. LEGISLATIVE TOOLS FOR THEPROTECTION OF TOCES -- EPILOGUE -- ACKNOWLEDGEMENTS -- REFERENCES -- INDEX -- Blank Page.
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    GEOMAR EBL
  • 2
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    Abundance of pteropods in the region of the Subtropical Convergence south of Africa during SAAMES-III in June and July 1993 (2013)
    PANGAEA
    Details
    Publication Date: 2023-08-01
    Keywords: Abundance per volume; BONGO; Bongo net; Date/Time of event; Depth, bottom/max; Depth, top/min; DEPTH, water; Event label; Latitude of event; Longitude of event; S. A. Agulhas; SAAMES-III; SAAMES-III_01; SAAMES-III_02; SAAMES-III_03; SAAMES-III_04; SAAMES-III_05; SAAMES-III_06; SAAMES-III_07; SAAMES-III_08; SAAMES-III_09; SAAMES-III_10; SAAMES-III_11; SAAMES-III_12; SAAMES-III_13; SAAMES-III_14; SAAMES-III_15; SAAMES-III_16; SAAMES-III_17; SAAMES-III_18; SAAMES-III_19; SAAMES-III_20; SAAMES-III_21; SAAMES-III_22; Subtropical North Atlantic; Taxon/taxa; Type; Uniform resource locator/link to reference
    Type: Dataset
    Format: text/tab-separated-values, 144 data points
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    DATA PANGAEA
  • 3
    Electronic Resource
    Electronic Resource
    Gut evacuation rates and pigment destruction in the Antarctic krill Euphausia superba (1996)
    Springer
    Marine biology 125 (1996), S. 47-54 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Krill grazing data collected during cruises in the region of the Antarctic Polar Front (S.A. “Agulhas” Voyage 70) and the South Georgia shelf (R.V. “Africana” Voyage 119) during the austral summer of 1993 were analyzed to estimate the variability of crucial parameters of the gut fluorescence technique in relation to food availability and krill feeding history. Gut evacuation rates (k) and passage or throughput times (1/k) varied in the ranges of 0.101 to 0.424 h-1 and 2.3 to 9.9 h and were strongly correlated (p〈0.001, r 2=0.98) to krill feeding activity (estimated as initial gut pigment content, G0) but not to ambient chlorophyll a concentration. A significant differences was found when k values derived from incubations in filtered seawater and low charcoal particle concentrations (0.4 to 0.8 mgl-1) were compared with values derived from krill fed high concentrations of charcoal (6 mgl-1). The efficiency of gut pigment destruction was among the highest recorded for zooplankton organisms, 58.1 to 98.4%, and did not covary significantly (p〉0.05) with ambient food concentration. However, the pigment lost per individual krill was strongly correlated with the total amount of pigment ingested (p〈0.001, r 2=0.99). We suggest that both gut evacuation rates and pigment destruction efficiency may be realistically estimated only when krill is allowed to continue ingesting particles uninterruptedly. Charcoal particle concentration should be equivalent to the in situ wet weight of total seston per unit volume. An objective criterion for the standardization of the measurement and calculation of k values is also proposed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00350759
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  • 4
    Electronic Resource
    Electronic Resource
    Summer distribution of netphytoplankton in the Atlantic sector of the Southern Ocean (1995)
    Springer
    Polar biology 15 (1995), S. 77-84 
    Details
    ISSN: 1432-2056
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The surface distribution of netphytoplankton (〉20 μm) in the Atlantic sector of the Southern Ocean was investigated along two transects during early and late austral summer 1990/91. Sampling was under-taken at intervals of 60′ of latitude between 34° and 70°S for the analysis of nutrients and for the identification and enumeration of netphytoplankton. Peaks in total diatom abundances were recorded at the Antarctic Polar Front (APF), in the vicinity of the South Sand wich Islands, in the marginal ice zone and in the neritic waters of the Atlantic sector of Antarctica. Cluster analysis indicates the existence of two major zones between Southern Africa and Antarctica. Diatom abundance increased south of the Antarctic Polar From along both transects, which can be partially explained by gradients of silicate concentration. Small chain-forming species (e.g. Fragilariopsis kerguelensis and Nitzschia lineata) dominated the diatom assemblages in early summer, while larger species, such as Rhizosolenia hebetata f. semispina and Corethron criophilum, dominated late summer diatom assemblages. The predominance of typically ice-associated forms in early summer suggests that the release of epontic cells during ice melt provides the initial inoculum for the netphytoplankton biomass. These small diatoms are subsequently replaced by larger species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00241045
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  • 5
    Electronic Resource
    Electronic Resource
    Seasonal variations in microzooplankton grazing in the region of the Subtropical Convergence (1996)
    Springer
    Marine biology 126 (1996), S. 433-442 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Microzooplankton grazing and community structure were investigated in the region of the Subtropical Convergence (STC) during three cruises of the South African Antarctic Marine Ecosystem Study (SAAMES) in austral summer (January/February 1993; December 1994/January 1995) and winter (June/July 1993). Chlorophyll a concentrations were consistently dominated by the 〈20 μm size fraction during all three cruises, while the contribution of the microphytoplankton (〉20 μm) to total chlorophyll a concentrations varied considerably between cruises. Microzooplankton communities were numerically dominated by protozoans comprising ciliates (aloricates and tintinnids) and dinoflagellates. Instantaneous growth coefficients of phytoplankton in the vicinity of the STC showed no seasonal trends. However, marked seasonal differences were observed in the size structure of the phytoplankton. The grazing impact of microzooplankton was highest when the 〈20 μm chlorophyll fraction contributed 〉95% of the total. Under these conditions, the instantaneous grazing rates ranged between 0.15 and 0.66 d-1. These correspond to daily losses of 14 to 48% of the inntial standing stock and between 45 and 81% of the potential primary production. At stations where microphytoplankton contributed significantly (∼-20%) to total chlorophyll concentrations, the grazing coefficients were lower, ranging between 0 and 0.53 d-1. This corresponds to a loss of 〈41% of the initial standing stock, or between 0 and 56% of the potential production. Our data suggest that microzooplankton represent the main grazing sink for production when the 〈20 μm chlorophyll size-class dominates total chlorophyll. These facts suggest that the efficiency of the biological pump may vary over time.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00354625
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  • 6
    Electronic Resource
    Electronic Resource
    Feeding association of the copepod Rhincalanus gigas with the tunicate salp Salpa thompsoni in the southern ocean (1997)
    Springer
    Marine biology 127 (1997), S. 479-483 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002270050036
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  • 7
    Electronic Resource
    Electronic Resource
    Feeding and predation impact of two chaetognath species, Eukrohnia hamata and Sagitta gazellae, in the vicinity of Marion Island (southern ocean) (1998)
    Springer
    Marine biology 131 (1998), S. 95-101 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The predation impact of the two chaetognaths Eukrohnia hamata and Sagitta gazellae on mesozooplankton standing stock were investigated in three depth layers during two 24 h stations occupied in the vicinity of Marion Island in late austral summer (April/May) 1986. The zooplankton community at both stations was dominated by small copepods (Oithona spp., Microcalanus spp.), which accounted for 〉95% of total zooplankton abundance. Chaetognaths comprised 〈2% of total zooplankton abundance. E. hamata constituted 〉95% of the total chaetognath stock. The general trend in both species was decreasing abundance with increasing depth, which appeared to be correlated to the distribution of copepods (r 2 = 0.45; P 〈0.05). Gut-content analysis showed that copepods (mainly Oithona spp., Calanus spp. and Rhincalanus gigas) and ostracods were the main prey of both species, accounting for 87 and 61% of the total number of prey in E. hamata and S.␣gazellae stomachs, respectively. In the guts of S.␣gazellae, pteropods (Limacina spp.) and chaetognaths were also well represented. The mean number of prey items (NPC) for E. hamata ranged from 0.02 to 0.06 prey individual−1 which corresponds to an individual feeding rate (Fr) of between 0.05 and 0.12 prey d−1. For S.␣gazellae, the NPC values were higher, varying between 0.04␣and 0.20 prey individual−1, or between 0.15 and 0.76 prey d−1. The daily predation impact of the two chaetognaths was estimated at between 0.3 and 1.2% of the copepod standing stock or between 7 and 16% of the daily copepod production. Predation by S. gazellae on chaetognaths accounted for up to 1.6% of the chaetognath standing stock per day.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002270050300
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  • 8
    Electronic Resource
    Electronic Resource
    Physical-biological coupling in the waters surrounding the Prince Edward Islands (Southern Ocean) (1999)
    Springer
    Polar biology 21 (1999), S. 135-145 
    Details
    ISSN: 1432-2056
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The results of a macro-scale oceanographic survey conducted in the upstream and downstream regions of the Prince Edward Islands in austral autumn (April/May) 1989 are presented. During the investigation, the Subantarctic Front, upstream of the islands, was shown to lie initially south at 46°38′S, while downstream, the front remained in a northern position of approximately 46°S. Surface expressions of the front show that the Subantarctic Front forms a zonal band, while the subsurface expressions (200 m) show a distinct meander in both regions. In the upstream region of the islands, the northern branch of the Antarctic Circumpolar Current, the Subantarctic Front, influenced by the shallow bathymetry, was deflected around the northern edge of the islands. Water masses in this region were shown to modify gradually from Subantarctic Surface Water (7°C, 33.75) to Antarctic Surface Water (5°C, 33.70) as the Polar Frontal Zone was crossed. Downstream of the islands a wake was formed resulting in the generation of broad, cross-frontal meanders. As a consequence, warm Subantarctic Surface Water from north of the Subantarctic Front was advected southwards across the Polar Frontal Zone, while cooler waters, which had been modified in the transitional band of the Polar Frontal Zone, were advected northwards. In the downstream region a warm eddy consisting of Subantarctic Surface Water was observed. Its generation is possibly due to baroclinic instabilities in the meandering wake. Zooplankton species composition and distribution patterns during the investigation were consistent with the prevailing oceanographic regime. Four distinct groupings of stations were identified by numerical analysis. These corresponded to stations found north of the Subantarctic Front, within the warm eddy, located in the Polar Frontal Zone, and those stations associated with the meander. The groupings were separated by the Subantarctic Front, which appears to represent an important biogeographic boundary to the distribution of warm-water zooplankton species. Warm eddies in the downstream region of the islands may represent an effective mechanism for transporting warm water species across the Subantarctic Front.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003000050344
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  • 9
    Electronic Resource
    Electronic Resource
    Phytoplankton production and biomass at frontal zones in the Atlantic sector of the Southern Ocean (1993)
    Springer
    Polar biology 13 (1993), S. 471-481 
    Details
    ISSN: 1432-2056
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A high resolution study of chlorophyll a and primary production distribution was carried out in the Atlantic sector of the Southern Ocean during the austral summer of 1990–91. Primary production (14C assimilation) and photosynthetic capacity levels at frontal systems were among the highest recorded during the cruise (2.8–6.3 mgC·m−3·h−1, and 1.3–4.7mgC·mgChl a −1·h−1, respectively). Blooms at ocean fronts were strongly dominated by specific size classes and species. This suggests that the increase in biomass was probably the result of an enhancement of in situ production by selected components of the phytoplankton assemblage, rather than accumulation of cells through hydrographic forces. This hypothesis is supported by the high variability of photosynthetic capacities at adjacent stations along the transects. Blooms (ca 2.7–3.5 mg Chl a·m−3) were found at three oceanic fronts (the Subtropical, Subantarctic and Antarctic Polar Fronts) during the early summer. These were equivalent to, or denser than, blooms in the Marginal Ice Zone and at the Continental Water Boundary. Seasonal effects on phytoplankton community structure were very marked. In early summer (December), netphyto-plankton (〉20 μm) was consistently the major component of the frontal blooms, with the chain-forming diatoms Chaetoceros spp. and Nitzschia spp. dominating at the Subantarctic and Antarctic Polar Fronts, respectively. During late summer (February), nanophytoplankton (1–20 μm) usually dominated algal communities at the main frontal areas. Only at the Antarctic Polar Front did netphytoplankton dominate, with the diatom component consisting almost exclusively of Corethron criophilum. An early to late summer shift of maximum phytoplankton biomass from north to south of the Antarctic Polar Front was observed. Spatial covariance between silicate levels and water-column stability appeared to be the main factor controlling phytoplankton production at the Antarctic Polar Front. Low silicate concentrations may have limited diatom growth at the northern edge of the front, while a deep mixed layer depth reduced production at the southern edge of the front.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00233138
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  • 10
    Electronic Resource
    Electronic Resource
    Contribution of salps to carbon flux of marginal ice zone of the Lazarev Sea, southern ocean (1998)
    Springer
    Marine biology 131 (1998), S. 25-32 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002270050292
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