Typescript. Includes vita and abstract. Bibliography: Includes bibliographical references (leaves 61-68).

The intertidal mussels. Perna perna and Choromytilus meridionalis co-occur on the southern coast of South Africa. Mussels ingest mixtures of bacteria. phytoplankton. zooplankton and detritus. with proportions varying according to availability. These bivalves filter similar-sized particles. which might result in interspecific competition. Carbohydrate-digesting enzymes of the mussels and their enteric bacteria. and bacteriolytic enzymes of the mussels were therefore examined to elucidate feeding ecology in these animals at an enzymatic level. Style enzymes of both species digested the storage carbohydrates amylose glycogen and laminarin, and the structural carbohydrate carboxymethyl cellulose (CMC). Differential rates of digestion of these carbohydrates suggests that Perna perna relies more on plankton (and possibly bacteria) than on detritus for food while Choromytilus meridionalis relies equally on all components of the seston. There may therefore be some degree of resource partitioning of the seston. The styles of P.perna had a lower specific enzyme activity. but higher protein content than those of C.meridionalis. P.perna could therefore release more glucose from a given concentration of substrate than C.meridionalis. The gut contents and tissue were examined microscopically to determine where the bacterial colonisation sites were. Bacteria were associated primarily with the gut contents but not the gut walls. of both species. The styles housed spirochaete bacteria (Crislispira sp), Perna perna housed large numbers of one species. while Choromytilus meridionalis had lower numbers of two species. Levels of infection differed between species and localities. Enteric (but not style) bacteria of Perna perna and Choromytilus meridionalis always digested the same carbohydrates as the mussels as well as the structural carbohydrates mannan and fucoidan. Activity was erratic on the structural compounds, carageenin and xylan, and absent on alginic acid or inulin. Activity on the storage carbohydrates by enteric bacteria from C.meridionalis was higher than by those from P.perna. This is probably related to the larger bacterial populations housed by C.meridionalis than by P.perna. Bacteriolytic activity by the digestive enzymes of Pema perna was higher than for Choromytilus. In P.perna it was due to a combination of different enzymes one of which is a true lysozyme. C.meridionalis did not produce a true lysozyme. Enzymes produced by the mussels and their enteric bacteria allow the mussels to utilise all components of the seston. Low endogenous enzyme activity by Choromytilus meridionalis, coupled with the high activity by its enteric bacteria, suggests that they rely more on bacterial activity to meet their dietary requirements than does Perna perna. The ability of enteric bacteria to digest carbohydrates which the mussels cannot indicates that the bacteria are endosymbiotic, although the sporadic nature of activity of some of the enzymes, and the fact that bacteria are associated with the gut contents, indicates that the relationship is only incidental.

Mytilus galloprovincialis is invasive on rocky shores on the west coast of South Africa where it has become the dominant intertidal mussel. The success of this species on the west coast and its superior competitive abilities, have led to concern that it may become invasive on the south coast at the expense of the indigenous mussel Perna perna. On shores where these species co-occur, there appears to be habitat segregation among zones occupied by mussels. M.galloprovincialis dominates the high-shore and P.perna the low-shore, with a mixed zone at mid-shore level. This study examined the factors responsible for these differences in distribution and abundance. The study was conducted in Plettenberg Bay and Tsitsikamma (70km apart) on the south coast of South Africa. Each site included two randomly selected locations (300-400m apart). A third mussel species, Choromytilus meridionalis, is found in large numbers at the sand/rock interface at one location in Plettenberg Bay. Aspects of settlement, recruitment, growth and mortality of juvenile and adult mussels were examined at different tidal heights at each site. Quantitative analysis of mussel population structure at these sites supported the initial observation of vertical habitat segregation. Post-larvae were identified to species and this was confirmed using hinge morphology and mitochondrial DNA analysis. Size at settlement was determined for each species to differentiate between primary and secondary settlement. Adult distribution of C.meridionalis was primarily determined by settlement, which was highly selective in this species. Settlement, recruitment and growth of P.perna decreased with increasing tidal height, while post-settlement mortality and adult mortality increased higher upshore. Thus all aspects of P.perna’s life history contribute to the adult distribution of this species. Presumably, the abundance of P.perna on the high-shore is initially limited by recruitment while those that survive remain prone to elimination throughout adulthood. M.galloprovincialis displayed the same patterns of settlement and recruitment as P.perna. However, post-settlement mortality in this species was consistently low in the low and high zones. Juvenile growth also decreased upshore, suggesting that M.galloprovincialis may be able to maintain high densities on the high-shore through the persistence of successive settlements of slow-growing individuals. The low cover of M.galloprovincialis on the lowshore appeared to be determined by adult interactions. M.galloprovincialis experienced significantly higher adult mortality rates than P.perna in this zone. There were seasonal variations in the competitive advantages enjoyed by each species through growth, recruitment or mortality on the low-shore. In summer, P.perna had higher recruitment rates, faster growth and lower mortality rates, while M.galloprovincialis had slightly higher recruitment rates and faster growth rates in winter. P.perna is a warm water species while M.galloprovincialis thrives on the cold-temperate west coast of South Africa. Therefore both species appear to be at the edge of their optimal temperature regimes on the south coast, which may explain the seasonal advantages of each. Nevertheless, P.perna has maintained spatial dominance on the low-shore suggesting that it may ultimately be the winner in competition between these species. M.galloprovincialis appears to have a refuge from competition with P.perna on the high-shore due to its greater tolerance of desiccation stress, while being competitively excluded from the low-shore. Warm water temperatures coupled with poor recruitment rates at most sites may limit the success of M.galloprovincialis on this coast.

Population dynamics of Perna perna in low shore mussel beds were investigated over a 15 month period at six sites along the south coast of South Africa, with particular reference to the effects of wave exposure. The degree of exposure was first quantitatively ascertained using the dissolution of cement blocks to measure average wave force and dynamometers to measure maximum wave force. The mean mass loss of the cement blocks was higher at Diaz Cross and Kwaai Hoek than at Mgwalana, Rufanes and Riet River. No data were available for Fish River. The mean maximum wave force encountered at Diaz Cross, Kwaai Hoek and Fish River was significantly higher (p<O.05) than that at Mgwalana, Rufanes and Riet River. These results allowed the former sites to be classified as exposed and the latter as sheltered. Early recruitment (1-5 mm) occurred throughout the year, but peaked significantly (p<0.05) from January 1995 to May 1996 on both shore types. Although mean recruit density (1-15 mm) was Significantly higher at the exposed (5 896.m⁻²) than the sheltered shores (2 986.m⁻²), some sites did not show this trend. Further investigation revealed that the densities of recruits (1-5 & 6-10 mm) were significantly higher on algae than on mussels (p<0.05). Adult densities (>15 mm) were positively correlated with recruit densities (1-5 mm) for both shore types (p<O.05). In tum, adult density (>15 mm) was significantly lower on exposed (mean of 3 348.m⁻²) than on sheltered shores (mean of 4 796.m⁻²) (p<O.05). Adult mussels on exposed shores had significantly higher mean and maximum lengths than those on sheltered shores (p<O.05). Biomass, which is a product of density and length, showed no significant difference between the two shore types (p>O.05). The effect of exposure on growth rate formed the focal point of this study and was determined using three different approaches. The first technique, mark-recapture, involved filing notches on the growing edges of mussels in the field. After 111 days, mussels were removed and the growth measured. The second approach used internal growth bands to measure growth rates, once the periodicity with which these bands were laid down was established. Thirdly, using Shepherd's length composition analysis (SLCA), growth rates were determined from length frequency distributions in 11 samples taken over 15 months. The general conclusion from all three approaches was that growth rate was twice as fast on the exposed shores as on the sheltered shores (p<O.05). A mean length (averaged from all three methods) of 47.06 mm was attained within the first year of growth at the exposed shores and 22.07 mm at the sheltered shores. There were however considerable differences among these approaches. The mark-recapture method predicted the lowest growth rates, followed by growth band method and lastly SLCA. The mean mortality index (Z.year⁻¹) for mussels was significantly (p<0.05) higher at the exposed shores (Z=1.81) than at the sheltered shores (Z=0.73). Consequently, the percentage survival rates per annum of mussels of all ages (total), 18 days to 6 months (juveniles) and 12 months to mortality (adults) was lower on the exposed than the sheltered shores. The survival rate of juveniles was as low as 0.71% per annum on the exposed shores and 9.29% per annum on the sheltered shores. The adult survival rate of exposed shore mussels was 11.78% per annum, considerably lower than that of sheltered shore mussels, 48.05%. The turnover rate on exposed shores was faster than on sheltered shores as the mean longevities were 2.6 and 6.7 years respectively. In conclusion, these findings showed that the effects of exposure on recruitment, growth and mortality are important in low shore mussel beds.

The aim of this study was to evaluate the methane potential of 35 kg of blue mussels in a batch amanaerobic two-stage dry digestion system (pilot-scale), which consists of aleach bed reactor (LB) and an up-flow anaerobic sludge blanket reactor (UASB). We monitored the process daily by measuring temperature, pH, COD, VFA, NH4+ gas flow rate and gas content. The temperature was approximately 30 C in the LB and 36 C in the UASB reactor. The applied OLR was 1.5 g COD/l*d. After 37 days process run, we obtained a total methamne yield of 0.64 Nm3 respectively 0.29 Nm3/kg VS, of that 70% in the LB reactor and 30% in the UASB reactor.

Applied zooarchaeology provides baselines which can be used in modern conservation biology to better understand how faunal communities have changed over time. This goal can only be accomplished, however, by first accounting for the multiple biases present within the archaeological record, and how they may affect sample representativeness. Taxonomic analysis was conducted on freshwater mussel shell from the late prehistoric (ca. A.D. 700 - 1200) Kinlock site, Sunflower County, Mississippi. Species-area curves and biodiversity indices demonstrate that random sampling of surface clusters of shell, up to about 4,000 valves, provides an adequate picture of the overall surface assemblage. Comparison of surface and subsurface contexts shows a highly significant difference in species numbers and proportions, indicating a need for multi-context sampling when dealing with archaeological shell deposits.

Rates of uptake of organic and inorganic suspended particulate material by suspension feeding bivalve molluscs have been studied since the nineteenth century (see Viallanes, 1892) . Studies have investigated molluscan feeding mechanisms, filtration capabilities, food assimilation and metabolism. The bulk of this work has been directed towards the mussel Mytilus edulis Linnaeus and the oyster Crassostrea virginica Gmelin (see reviews by Galtsoff, 1964; Ali, 1970; Jorgensen, 1975; 1976; and Winter, 1978). More recently the growth of mussels, oysters, clams and scallops has been quantitatively studied in controlled systems to assess the biological potential of these molluscs in an aquaculture setting (Hartman et al., 1973; Tenore & Dunstan, 1973; Tenore et al., 1973; Kirby-Smith & Barber, 1975; Walne & Spencer, 1974; Epifanio & Ewart, 1977; Winter, 1978). Direct and indirect methods for estimating filtration rates of molluscs (Ali, 1970) have yielded such a wide range of results that the validity of comparisons between different studies is sometimes questionable . Variables such as the mollusc species and size, as well as the nature and concentration of the test suspension contribute to differences in observed filtration rates. The present study simultaneously examined three mytilid speeies of comparable size (85-125 mm shell length) . Each mussel species was tested under the same conditions for its ability to filter and assimilate the unicellular algae Dunaliella primolecta Butcher at suspensions of 5, 12, 25 and 50 x 106cells/1. Filtration rates and food assimilation were determined in test chambers incorporating a new flow-through design which eliminated the possibility of recirculation of the algae test suspension. In previous studies recirculation of the test suspension has occasionally resulted in the under-estimation of filtration rates. Growth comparisons were made among individuals of each species held under the same set of environmental conditions. Two of the mussel species examined in this study, Mytilus edulis L. and Perna canaliculus Gmelin, are presently under cultivation as a human food source. The third species, Mytilus catifornianus Conrad, may be viewed as a potential candidate for aquaculture due to its size, abundance and value as a source of protein. The California mussel, M. catifornianus, is found along the west coast of North America from the Aleutian Islands to Baja California (Soot-Ryen, 1955). The bay mussel, M. edutis , is widespread in the northern and southern hemispheres (Stubbings, 1954). The green-lipped mussel, P. canaliculus, is found throughout New Zealand waters where it colonizes both exposed rocky coasts and quiet bays (Morton & Miller, 1968; Paine, 1971).

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To determine the effects of different algal diets on freshwater mussels, tissues of Elliptio complanata were sampled for physiological, somatic, and gametogenic condition from August 1999 to May 2000. Treatments included mussels fed Scenedesmus quadricauda (S), Neochloris oleoabundans (N), a no feed treatment (NF), and a reference group of mussels from the Nottoway River (NR), Virginia. The levels of protein and glucose differed among treatments (p<0.0001), but glycogen and percentage tissue moisture did not (p>0.17). Production of ripe and developing gametes differed significantly among treatments (p=0.001), but stage of gamete development did not (p=0.70). Lipid levels and muscle fiber areas of treatment groups differed significantly (p<0.0001). Results of the feeding trial indicate that S. quadricauda is a suitable feed for E. complanata, but future experiments should identify algal species higher in carbohydrates for a mixed algal diet. To determine sex and stage of gametogenesis, tissue histological sections from gonads of Villosa iris and Utterbackia imbecillis were evaluated. Occurrences of oogenic, spermatogenic, and hermaphroditic tissues were summarized in frequency tables. Visceral sites from which similar tissues were collected from conspecific specimens were evaluated for gametogenic stage. Sex was accurately determined in the central, visceral portion V. iris and female regions of U. imbecillis; and spermatogenic tissue was consistent in the dorsal-anterior areas of U. imbecillis. These areas also provided accurate determination of gamete stage in specimens. Reproductive asynchrony was observed among males and females (p<0.02). Male regions of U. imbecillis showed gamete stage characterized by mature and developing spermatogenic tissue, while 2 groups of mussels were showed oogenic development characterized by mature oocytes and resorption of gametes. Male V. iris showed early gamete development without mature spermatozoa, and 2 groups of female V. iris showed mature and developing gametes and resorption of gametes. Protocols for biopsy tissue collection from selected visceral areas were developed for U. imbecillis and V. iris for sex determination and staging of gametogenesis. The application of this biopsy protocol should be considered population specific, and protocols appropriate for other populations and species should be developed with methods of this study. / Ph. D.