Coral Recruit-Algae Interactions in Coral Reef Lagoons Are Mediated by Riverine Influences

Coral recruit and algae abundance and diversity were studied in Kenyan reefs to determine the influence of terrestrial discharge (nutrients and sediments) and the recovery potential of coral reefs after disturbances. Reefs affected by sediments and nutrients were found to have high total, turf, and macroalgae but reduced coralline algae abundance and coral recruit density. Interestingly, this response was found to be the greatest in reefs close to nutrient sources relative to “pristine” reefs and those affected simultaneously by sediments and nutrients. Further, enhanced levels of brown algae and pocilloporid recruits were observed in reefs affected by terrestrial run-off whereas acroporid recruit, coralline, and calcareous algae abundance was high in reefs under low terrestrial input. Our results show that whereas increased sediment levels negatively affect coral recruit density individually, their interaction with nutrients improves recruit density in reefs simultaneously affected by sediment and nutrients. These findings suggest that the assessment of local factors that enhance inhibitory and those that suppress promotional processes involved in coral settlement and recruitment is an important aspect to consider in the conservation and management of coral reefs in the face of local anthropogenic stress as well as future climate disturbance dynamics and their interaction

Effect of processing and microbial enzyme treatment on the nutritive value of canola meal for rainbow trout (Onchorynchus mykiss)[

Salmonids (trout, salmon and charr) require high dietary concentrations of protein, and they utilize protein and lipids as their principle sources of dietary energy. In culture conditions the protein is mainly supplied by fish meal and other products from the capture fishery. However, the high cost, and variability in fish meal quality due to processing and storage conditions, dissimilar raw material quality, as well as fluctuations in the supply of fish meal are major concerns. Feed accounts for 40% to 60% of the operating costs of salmon fanning. Much of this cost is associated with the inclusion of fish meal as the predominant protein source. Replacement of at least some of this fish meal by cheaper plant protein products is one way of reducing these costs. This study was undertaken to assess the chemical composition and potential nutritive value (digestibility) of canola protein products developed by processing canola meal by substituting fish meal in salmonid diets, with rainbow trout (Oncorhynchus mykiss) in fresh water as the test animal. Sieving, methanol/ammonia treatment and the use of three types of enzyme (Phytase, SP- 249, Alpha-Gal) treatments, singly or in various combinations, were employed in this study. In addition, a commercially-produced canola protein isolate (CPI) was also evaluated for potential nutritive value. It was hoped that one of these products would be potentially suitable as a replacement for fish meal. The results indicated that sieving canola meal did not have any significant influence on its chemical composition. Treatment of canola meal with methanol/ammonia however, decreased the amount of total glucosinolates by over 80%, and lowered the levels of phenolic compounds but this protocol increased the concentration of phytate. Application of carbohydrases did not result in any appreciable improvement in the fibre composition of the meals, although it did lead to increases in the protein content and levels of amino acids, and to decreases in the levels of glucosinolates and phytate. Low levels of glucosinolates were detected in all the canola protein products that received the enzyme treatments either singly or in combination. The processing methods used in the production of canola protein isolate (CPI) significantly improved the nutrient composition of the resultant product. Levels of total glucosinolates, protein, gross energy and phytate of the canola protein isolate (CPI) were 1.95 umol/g, 90.8% , 24.4 MJ/kg and 4.3 umol/g, respectively compared to 8.95 umol/g, 36.3%, 19.6 MJ/kg and 45.5 umol/g, of commercial canola meal. In a three-week digestibility experiment, the effect of processing canola meal on the digestibility of dry matter, protein and energy by 74 g rainbow trout was assessed using a modified "Guelph system" of faecal collection. The canola products were included at 30% of the diets (70 % reference: 30% test canola protein product). Each of the test diet treatment was assigned to triplicate groups of fish using a completely randomized block design with chromic oxide (0.5%) as an indigestible marker. The fish were hand fed to satiation twice daily in special designed 150 L fibre glass tanks supplied with fresh running water (9.9 °C to 11.0 ° C) at a flow rate of 4-5 L/min. Processing methods had variable effects on the apparent nutrient (dry matter, protein and energy) digestibility coefficients. All the laboratory processing protocols employed with a view to enhance the nutritional value of canola meal had significant negative effects on dry matter digestibility coefficients and generally negligible effects on protein digestibility. There were however, significant reductions in protein digestibility coefficients in the meals treated with SP- 249 (77.4%) alone or in combination with Alpha-Gal (79.5%) relative to untreated canola meal (88.1%). Energy digestibility coefficients and the digestible energy contents of the test canola protein products were the least affected by the processing methods selected for this study. However, treatment of canola meal with either methanol/ammonia or combination of carbohydratedegrading enzymes had negative effects on the energy digestibility coefficients and digestible energy contents. For instance, these two parameters were lowered by about 14 percentage units and 3 Ml/kg in the ammoniated canola meal and by about 17 percentage units and 2.7 MJ/kg for the meal treated with the two carbohydrate-degrading enzymes. Digestibility coefficients for dry matter, protein and energy for the canola protein isolate (CPI) were 77.1%, 97.6%, and 84.7 %, respectively, and it is noteworthy that all these values were much higher than those values found for the untreated and treated canola meals.Land and Food Systems, Faculty ofGraduat

Terrestrial discharge influences microbioerosion and microbioeroder community structure in coral reefs

Microbioerosion rates and microbioeroder community structure were studied in four Kenyan protected coral-reef lagoons using shell fragments of Tridacna giant clams to determine their response to the influence of terrestrial run-off. Fourteen different microbioeroder traces from seven cyanobacteria, three green algae and four fungi species were identified. The river discharge-impacted reef and ‘pristine’ reef showed similar composition but higher microbioeroder abundance and total cyanobacteria- and chlorophyte-bioeroded areas when compared with the other study reefs. Cyanobacteria dominated during the north-east monsoon (NEM) relative to the south-east monsoon (SEM) season, with algae and cyanobacteria being major microbioeroders in the river-impacted and pristine reefs. The rate of microbioerosion varied between 4.3 g CaCO3 m−2 y−1 (SEM) and 134.7 g CaCO3 m−2 y−1 (NEM), and was highest in the river-impacted reef (127.6 g CaCO3 m−2 y−1), which was almost double that in the pristine reef (69.5 g CaCO3 m−2 y−1) and the mangrove-fringed reef (56.2 g CaCO3 m−2 y−1). The microbioerosion rates measured in this study may not be high enough to cause concern with regard to the health and net carbonate production of Kenya’s coral reefs. Nevertheless, predicted increases in the frequency and severity of stresses related to global climate change (e.g. increased sea surface temperature, acidification), as well as interactions with local disturbances and their influence on bioerosion, may be increasingly important in the future.Keywords: carbonate substrates, climate change, coralline algae, East Africa, microbial euendoliths, nutrients, river run-off, sediment

Effects of river sediments on coral recruitment, algal abundance benthic community structure on Kenyan coral reefs

The effects of sediment concentration and season on coral recruitment algal abundance nd benthic community structure were studied in Kenyan coral reef lagoons to determine their potential influence on coral recovery. Nutrient levels and recruit numbers were higher during the southeast monsoon (SEM) than during the northeast monsoon (NEM) season and in sediment-exposed compared to nonsediment exposed reefs. Mean algal biomass also exhibited the same seasonal trend (except at one site), but was higher in the non-sediment exposed reef compared to the other reefs. Corals in the sediment exposed reef exhibited morphological differences relative to the other reefs: fewer corymbose and plate-like but more branching, massive and solitary forms and increased colony and corallite sizes. However, sediments did not suppress coral recruitment rates. These morphological changes coupled with the interaction between biological and physico-chemical characteristics have important ecological and geological implications: by potentially modifying calcium carbonate production and ameliorating the adverse effects of climate induced stress events, this may minimize coral mortality and enhance reef recovery.Key words: Algal biomass, coral recruitment, hydrodynamics, coral morphology, seasonality, sediments