Pearl Oyster Farming Research Articles

Advancing The Blue Economy Through Sustainable Mariculture: The Prospect of Pearl Oyster and Sponge Cultivation in St. Vincent and The Grenadines

The Blue Economy is estimated to be worth over USD 2.5 trillion annually, or almost 3% of the world’s GDP in 2020. St. Vincent and the Grenadines (SVG) in the Caribbean region has a vast and rich marine space that is underutilized. This study aimed to explore the feasibility of pearl oyster and sponge farming to advance the country’s Blue Economy through sustainable mariculture. A qualitative approach was applied, using a literature review and thematic analysis of data gathered through semi—structured interviews and focus group discussions with relevant stakeholders. Among several species evaluated, the result of the study revealed that the Pinctada imbricata oyster species and Hippospongia lachne sponge species are the most suitable for cultivation in SVG coastal waters, specifically in the Ashton Lagoon of Union Island. The study concluded that while there is strong support from the stakeholders in SVG for pearl oyster and sponge farming in the country, challenges still exist. Nevertheless, it has been found that by learning and adopting the strategies of the leading Small Island Developing States (SIDS) in the Blue Economy development combined with the critical enablers such as meticulous planning, stakeholder collaboration, establishment of legal frameworks, and ecosystem—based management, pearl oyster and sponge mariculture in the identified location in SVG could potentially aid the expansion of the country’s Blue Economy.

THE ENVIRONMENTAL PARAMETERS SUITABILITY FOR MULTISPECIES-BASED MARICULTURE IN PONGOK ISLAND WATERS, BANGKA BELITUNG

Pongok Island possesses small islands surrounded by waters with some primary commodities of sea farming. Seeking appropriate locations for marine aquaculture is a careful planning step to acquire optimal results. The sustainability of sea farming areas should be set based on considering species for easy implementation. This research aimed to analyse the area's suitability for aquaculture activities of seaweed cultivation, rearing groupers, and lobsters in floating net cages, and pearl oyster farming. This research occurred from June to November 2022 in Pongok Islands, South Bangka Regency, Indonesia. The method used in this research consisted of parameters weighting and scoring for cultivating seaweeds, groupers, or lobsters utilizing floating net cages and pearl oysters. Sea water samples analysis was processed in the Marine Science Laboratory of Bangka Belitung University and PT Global Quality Analytical, Bogor – West Java. Collected data were then scaled based on expert justification of scaling priority on aquaculture suitability. The mapping area of sea farming locations based on potential resources was then determined using map software. This research indicates that cultivating seaweeds is recommended to be established in two stations, 1 (149.79 ha) and 2 (186.46 ha), that are very suitable (S1) and the suitable (S2) categories, respectively. Station 3 (325.41 ha) and 4 (4.11 ha) are grouped into very suitable (S1) categories for pearl oysters and groupers or lobsters using floating net cages, respectively. The total estimate for sea farming in the waters of Pongok Island is 665.77 ha. Allocating seawater spaces should be assigned for sustainable fishery management. Maps of area suitability for sea farming can obviate conflicts in seawater areas.

The first reporting of prevalence Vibrio species and expression of HSP genes in rayed pearl oyster (Pinctada radiata) under thermal conditions.

The main goal of the present study was to evaluate the influence of thermal exposure on Vibrio population and HSP genes expression (HSP 90, HSP70, and HSP20) in rayed pearl oyster (P. radiata). To this end, the oysters were reared for 30 days at temperatures of 22°C (control), 25°C, 27°C, and 29°C. The results showed that five dominate Vibrio strains including Vibrio hepatarius, V. harveyi, V. alginolyticus, V. parahaemolyticus, and V. rotiferianus were identified. The highest population of V. parahaemolyticus, V. alginolyticus, and V. harveyi, was found in 29οC group. According to real-time PCR, mantle exhibited the highest expression levels of HSP20, HSP70, and HSP90 genes. A higher level of HSP20 expression was observed at high temperatures (25°C, 27°C, and 29°C) in the gonad and mantle compared to the control group (22°C) while decrease in HSP90 expression level was recorded in 25°C, 27°C, and 29°C groups. HSP20 expression level in adductor muscle was remarkably down-regulated in 27°C and 29°C groups. In this tissue, HSP70 was detected at highest levels in the 29οC group. In mantle, HSP90 gene expression was lowest at 22°C water temperature. Several Vibrio strains have been identified from pearl Gulf oyster that haven't been previously reported. The identification of dominant Vibrio species is essential for epidemiological management strategies to control and prevent Vibrio outbreaks in pearl oyster farms. The expression pattern of HSP genes differs in rayed pearl oyster tissues due to differences in their thermal tolerance capability and physiological and biological characteristics. The present study provides useful molecular information for the ecological adaptation of rayed pearl oysters after exposure to different temperature levels.

Analysis Of Water Quality Conditions In Pearl Oyster (Pinctada maxima) Hatcheries in Karangasem Bali

Indonesia has a high potential for pearl oyster farming due to its diverse marine habitats, warm waters, and abundant supply of seaweed, which is the preferred food for pearl oysters. Indonesia is home to several species of pearl oysters, including the Pinctada maxima, which are prized for their large size and the quality of their pearls. Water quality plays a crucial role in the cultivation of Pinctada maxima. Factors such as temperature, pH, salinity, dissolved oxygen levels, and the presence of pollutants and pathogens can all impact the health and survival of Pinctada maxima. In addition to feed quality and seed availability, good water quality management is the key to the success of this biota seedling. This research was carried out by measuring parameters including temperature, salinity, pH, and dissolved oxygen levels in the waters temporally in the morning and evening every day of cultivation. Variables of ammonia, nitrite, total suspended solids, total bacteria, and vibrio bacteria were carried out once a week. The results of temperature measurements range from 28.2-290C. Measurement of total suspended solids 0 mg/l. pH measurements ranged from 8.1-8.3. Dissolved oxygen measurements ranged from 4.16-4.27 mg/l. Salinity measurements obtained results of 35 ppt. Ammonia measurements range from 0-1.55 mg/l. Nitrite measurements range from 0.012-0.026. Measurement of total bacteria obtained <1 X 101 cfu/ml from all samples. Measurement of total vibrio yielded <1 X 101 cfu/ml from all samples. Based on the research that has been done, the results show that water quality is still in the optimal range for pearl oyster (Pinctada maxima) hatchery activities.

The Application of an Artificial Neural Network to Quantify Anthropogenic and Climatic Drivers in Coastal Phytoplankton Shift

The overlapping effect of anthropogenic activities and climate change are major drivers for a shift in coastal marine phytoplankton biomass. Linear regression analyses are not sufficient to detect the nonlinear relationship between complex environmental factors and phytoplankton shift. Here, an Artificial Neural Network (ANN) model is applied to quantify the relative contribution of pearl oyster farming, temperature and rainfall on phytoplankton increases in Cygnet Bay, Australia. The result shows that increased oyster farming ranks among the most important factors for phytoplankton increases, with a relative importance of 54% for diatoms and 74% for dinoflagellates; temperature plays a second important role with a positive impact on diatoms (relative importance of 25%) but a negative impact on dinoflagellates (relative importance of 19%); rainfall is the least important which enhances diatom biomass only (relative importance of 21%). Our ANN analysis provides a useful approach for quantifying the complex interrelationships affecting phytoplankton shift.

THE CHARACTERISTICS OF MARINE ENVIRONMENT AND SUITABILITY FOR PEARL OYSTER (Pinctada maxima) CULTIVATION IN BARRU REGENCY

The coastal waters utilization that has potential to be developed in Barru regency is the cultivation of pearl oysters (Pinctada maxima). However, to get the maximum results, site selection through inventory activities and mapping of potential of the waters is an important early stage to do. The purpose of this study was to assess the suitability of Barru regency coastal waters for pearl oysters (Pinctada maxima) farming. The method used in the current study were the characteristics analysis, plankton abundance SID analysis (Simpson's index of diversity), and suitability analysis of pearl oyster farming by weighting. Conditions of physical parameters i.e tidal waters was characterized by a mix tidal or semidiurnal tides which has two high tides and two low tides in each tidal day. The waters current ranged from 14 until 69 cm/s. Water depths contour ranged from 5 until >200 meters and the water temperature was relatively high at the first transitional season (May) which ranged from 30.1 to 31.6 0C. Chemical parameters, such as salinity, dissolved oxygen, pH, and nitrate still met the water quality standard of marine waters. However, the posphat concentration in the estuary had exceeded the level of quality standard , i.e >0.015 mg/L. Barru coastal waters that had the potential for pearl oysters (Pinctada maxima) farming with a very appropriate status has an area of 3,201 ha. Keywords: Coastal, Pearl oyster farming, Suitability, Environmental

THE CHARACTERISTICS OF MARINE ENVIRONMENT AND SUITABILITY FOR PEARL OYSTER (Pinctada maxima) CULTIVATION IN BARRU REGENCY

The coastal waters utilization that has potential to be developed in Barru regency is the cultivation of pearl oysters (Pinctada maxima). However, to get the maximum results, site selection through inventory activities and mapping of potential of the waters is an important early stage to do. The purpose of this study was to assess the suitability of Barru regency coastal waters for pearl oysters (Pinctada maxima) farming. The method used in the current study were the characteristics analysis, plankton abundance SID analysis (Simpson's index of diversity), and suitability analysis of pearl oyster farming by weighting. Conditions of physical parameters i.e tidal waters was characterized by a mix tidal or semidiurnal tides which has two high tides and two low tides in each tidal day. The waters current ranged from 14 until 69 cm/s. Water depths contour ranged from 5 until >200 meters and the water temperature was relatively high at the first transitional season (May) which ranged from 30.1 to 31.6 0C. Chemical parameters, such as salinity, dissolved oxygen, pH, and nitrate still met the water quality standard of marine waters. However, the posphat concentration in the estuary had exceeded the level of quality standard , i.e >0.015 mg/L. Barru coastal waters that had the potential for pearl oysters (Pinctada maxima) farming with a very appropriate status has an area of 3,201 ha.
 Keywords: Coastal, Pearl oyster farming, Suitability, Environmental

Assessment of an alternative Pinctada margaritifera spat collector in French Polynesia

Plastic waste in the oceans is a growing concern due to its size diversity, its ubiquitous nature and its impact on both marine organisms and ecosystems. While threatened by this marine plastic litter, the aquaculture industries also represent one of its major sources. In French Polynesia, black-lip pearl oyster (Pinctada margaritifera) farming is no exception. Wild spat collection has been described as a source of pollution because of the numerous particularly fragile and brittle shade-mesh plastic collectors used locally and often mismanaged when no longer usable. Thus, with the aim of helping to reduce this pollution, the present study is focused on the assessment of reusable plate collector as a potential alternative. We tested, using an in situ approach, the influence of the collecting surface position (i.e. horizontal vs vertical), plate color (i.e. black vs orange) and density (i.e. 25 plates vs 50 plates) on Pinctada margaritifera and Pinctada maculata spat settlement. Our results showed that 50-plates collectors, whatever their color and position, were more efficient to collect both kinds of spat than shade-mesh collectors (P < 0.0001). They also induced a higher number of Pinctada margaritifera spat than on the 25-plates collection device although there was no significant difference in numbers of Pinctada maculata spat (P < 0.0001). However, every type of plate collector presented a decreased mean length of the spat collected (P < 0.0001) compared to the shade-mesh collector. Furthermore, horizontal positioning of the collecting surface greatly improved the spat numbers on plate collectors (P < 0.0001) although there was no effect on shade-mesh collectors (P > 0.05). Finally, our results indicated that, among all the devices tested, the black horizontal 50-plates collector was the most efficient to collect spat and particularly Pinctada margaritifera. These first findings thus tend to suggest that these black re-usable plate collectors could be an efficient alternative to the currently used shade-mesh collectors.

STRATEGI PEMBERDAYAN PEMUDA MELALUI BUDIDAYA TIRAM MUTIARA DI NEGERI HATUSUA KECAMATAN KAIRATU

Hatusua is a country located in West Seram district and is one of the pearl oyster farming locations. Pearl oyster cultivation in Hatusua country has been around since 2007. The cultivation methods used are KJA and longline methods. Pearl oyster cultivation in the country of Hatusua is also one of the village programs carried out based on the cooperation of the village government with PT Globalindo Mutiara where the company is a company engaged in the fisheries sector, namely pearl shell cultivation. The existing empowerment program requires a more focused development on improving the welfare of the community (youth) without neglecting various aspects, both socio-economic, technical and institutional. The purpose of this paper is to determine youth empowerment development strategies through cultivation of mutaira oysters in Hatusua country. Data analysis using process hierarchy analysis (AHP) includes socio-economic, technical and institutional aspects. Selection of the main criteria chosen by respondents in the AHP assessment based on a comparison of the three main criteria as the most selected criteria for the empowerment strategy were the socio-economic aspects of 41.2% followed by technical aspects of 32.6% and institutional aspects of 26.2%. The combination of the synthesis of the assessment results in the AHP calculation shows that the sequence of the implementation of the youth empowerment strategy is employee wages, family dependents, land suitability, worker skills, land area, business experience, state regulations, government programs, and support from the Marine and fisheries Service.

Length-weight relationship and relative condition factor of pearl oyster, Pinctada fucata martensii, cultured in the Tieshangang Bay of the Beibu Gulf, Guangxi Province, China

Tieshangang Bay in the Beibu Gulf, Guangxi of China, is a strategic location for pearl farming. Although water pollution has been reported in this bay but the general health of the pearl oyster, Pinctada fucata martensii, farmed there has never been assessed. The present study examined the condition of P. fucata martensii farmed in the Tieshangang Bay by analyzing its length-weight relationship (LWR) and relative condition factor (RCF). A total of 111 specimens were sampled for measuring their shell height and total weight for determining the LWR and RCF. The coefficient of correlation of the LWR was high (R2 = 0.93), significant at 0.01 level. Negative allometric growth (b = 2.7048) was observed. However, P. fucata martensii achieved the expected growth in terms of weight, as determined through the RCF (mean 1.13). Negative allometric growth is commonly reported on the wild Pinctada spp. collected from different regions. Apparently, the water pollution in the Tieshangang Bay did not compromise the general health of the pearl oyster cultured there. Nevertheless, further study on the farm’s surrounding water quality and plankton availability is necessary to investigate the interaction between the growth of the oyster and its culture environment. In conclusion, the P. fucata martensii farmed in the Tieshangang Bay was considered healthy and the bay is still suitable for pearl oyster farming.

Growth and survival of host pearl oyster Pinctada fucata martensii (Dunker, 1880) treated by different biofouling-clean methods in China

Pearl oyster Pinctada fucata martensii is an economically important species farmed to produce round nucleated pearl in China. However, pearl oyster shells are commonly exposed to biofouling, which is manually cleaned. This study experimentally evaluates the effects of biofouling cleaning by Siganus fuscescens (Houttuyn, 1782) foraging on growth performance and pearl traits of host pearl oyster P. fucata martensii. Three groups designated as EG1, EG2 and EG3 were set in the experiment. In EG1, biofouling was manually cleaned every 2 weeks and oysters were cultured in natural sea conditions. In EG2, biofouling was cleaned by foraging behavior of S. fuscescens every 2 weeks and oysters were cultured in natural sea conditions. In EG3, oysters were farmed in the net cage where S. fuscescens were stored. The survival rate of EG2 was higher than those of EG1 and EG3 and the daily growth rates of length and weight of shell and the thickness and weight of pearl of EG3 were significantly larger than those of EG1 and EG2. The survival rate, daily growth rates of the length and weight of shell, and thickness and weight of pearl were not significantly different between EG1 and EG2. This study suggested S. fuscescens foraging could evidently improve survival of host pearl oyster, which is promising to improve pearl yield in pearl oyster farms in China.

KOMPOSISI JENIS BIOFOULING PADA TIRAM MUTIARA (PINCTADA MAXIMA) DI LAHAN BUDIDAYA PT. AUTORE PEARL CULTURE LOMBOK

Cultivation of pearl oyster Pinctada maxima types are increasingly in demand in Indonesia. This oyster living and concentrated on waters that have coral reefs and sandy rubble. Oyster cultivation is very promising given pearls produced have a high economic value. Eventhough, pearl oyster farming efforts not always performing well because there is a possibility of oysters will get the disease and even death. One reason is their biofouling attached to the basket or on the oyster shell is maintained. The existence and amount of biofouling usually varies depending on the time and conditions of the waters where the cultivation have been. This study aims to determine the types of biofouling were found at three different sites located on land cultivation PT. Pearl Culture Autrore Lombok. Study sample is limited to biofouling found on new and used baskets and pearl oyster shells P. maxima. The main parameters measured were the species composition and abundance, while the supporters of the parameters measured were temperature, salinity, current speed, the brightness of the waters and TSS (Total Suspended Solid). The results found 36 types of biofouling, including 21 types of animal groups with six phyla (arthropods, bryozoans, annelids, cnidarians, sponges and molluscs), and 15 species of the plant with two divisio (Spermatophyta and Thallophyta). In addition, it was found that water conditions have an influence on the biomass and the number of types of biofouling and the distance between substations in each station does not have a significant influence on biomass and the number of types of biofouling.Keywords: Biofouling, Pearl Oyster (Pinctada maxima ), PT. Autore Pearl Culture Lombok

Spatial distribution and biophysics chemistry characterization of Pearl Oyster farming in Semau Strait, East Nusa Tenggara

Pearl oyster is one of marine organisms which has high of economic value. One of Indonesia region that potential for pearl oyster farming activity is Semau Strait-East Nusa Tenggara. The purpose of this study is mapping and characterize spatial distribution based on biophysics chemistry condition of pearl oyster farming. Mapping using Geographic Information System (GIS) tools, while grouping and characterize using hierarchical clustering and Mann-Whitney method. Grouping based on character similarity of biophysics chemistry divided the stations distribution into three groups: Group I is excellent group, Group II is good group and Group III is bad group for pearl oyster farming. Group I is excellent area because it has the highest values of dissolved oxygen, chlorophyll-a, and phytoplankton abundance. Group III is bad area because it temperature is high relatively.

Paleo-ecological analyses to assess long-term environmental effects of pearl farming in Western Australia

Small environmental disturbances accumulating over a long period of time may cause a regime shift in marine ecosystems, particularly in sensitive oligotrophic waters. Pearl oyster aquaculture, which has a 50 yr history in Australia, has been regarded as an anthropogenic activity with low environmental risk. To assess the long-term environmental effects of pearl oyster farming, sediment cores taken in Cygnet Bay, Western Australia, were used to reconstruct environmental processes covering an approximately 90 yr period. Biogeochemical parameters in sediment cores from inside and outside a pearl farming area displayed contrasting characteristics over time. Total organic carbon, total nitrogen, biogenic silica (BSi), and fine-grained sediment at the farming site displayed significant increases with the expansion of oyster stocking. In contrast, only small variations in response to climatic signals (rainfall and temperature) occurred over time in the cores outside the farm. The variation in the C:N ratio, delta C-13 and delta N-15 ranges over time suggested that increased organic matter was mainly contributed by autochthonous sources rather than terrestrial input. The sequential t-test for a regime shift detected approximately 2-to 3-fold increases in organic matter, 1-to 5-fold increases in silt proportion and 2-to 5-fold increases in BSi concentrations after pearl oyster farming, in contrast to the control site. The rapid development of modern long-line culture since the late 1980s is presumed to have been the dominant driver of environmental changes in sediments. The results provide insight into the magnitude of environmental change which can occur over decades as a result of even minimal anthropogenic activity.

Nutrient regeneration in the water column and at the sediment–water interface in pearl oyster culture (Pinctada margaritifera) in a deep atoll lagoon (Ahe, French Polynesia)

The aim of this work was to provide a first estimation of the overall contribution of pearl oyster culture to nutrient regeneration in a deep atoll lagoon. Nutrient release by pearl oyster culture in the water column and nutrient fluxes at the sediment–water interface were compared in two contrasted conditions (i.e. under the influence or not of pearl oyster farming) in the Ahe atoll (French Polynesia). Nitrogen flux intensity was higher in the water column than at the benthic interface. Nitrogen was released at a rate of 31.36 μmol h−1 m−2 in the water column and 12.05 μmol h−1 m−2 at the sediment–water interface. Average phosphorus flux was 2.85 μmol h−1 m−2 at the sediment–water interface and 2.16 μmol h−1 m−2 in the water column. In this deep lagoon, pearl oyster culture exerted more influence in the pelagic compartment than at the benthic interface where flux rate seemed not to be influenced by the presence of pearl oyster culture. These results demonstrate that it is essential to study these two interfaces in concert when assessing the impact of suspended shellfish farming on nutrient dynamics. Overall, the impact of pearl oyster culture may stimulate phytoplankton growth near cultivation areas through the rapid recycling of inorganic nutrients.

THE RELATIONSHIP BETWEEN SEASON VARIATIONS AND DEPTH LEVEL ON THE GROWTH AND SURVIVAL RATE OF PEARL OYSTER SEEDS (Pinctada maxima) IN KAPONTORI BAY, BUTON ISLAND

The pearl oyster (P. maxima) farming particularly in the Kapontori Bay, Buton Island waters and in other areas had complained for the mass mortality of pearl oysters saplings on the shell width between 3-4 cm. The mass mortality, was allegedly as a result of changing in environmental conditions and triggered by the shift in seasons. This research aimed to determine the effect of seasonal variations in water conditions at different depth levels on growth and survival of seedlings of pearl oysters conducted on March 27, 2007 to February 28, 2008. This research was very useful for pearl oyster farming in an effort to suppress the mass mortality rates based on the appropriate level of depth and seasons. The variance analyses showed that depth levels affected the survival rates of the pearl oyster seeds significantly (P&lt;0.01). Based on honest significantly difference test, it also showed that the percentage number of survival rate was found higher within the depth of 2m (93.33%). Based on the relationship analyses between length and weight of shell body in all depths indicated a similar growth pattern of minor allometric (b&lt;3). The growth, survival rate, and environmental conditions based on depth levels on pearl oyster saplings were discussed in this paper. Keywords: Seasonal variation, survival rate, growth, pearl shell (P. maxima), depth level

THE RELATIONSHIP BETWEEN SEASON VARIATIONS AND DEPTH LEVEL ON THE GROWTH AND SURVIVAL RATE OF PEARL OYSTER SEEDS (Pinctada maxima) IN KAPONTORI BAY, BUTON ISLAND

&lt;p&gt;The pearl oyster (&lt;span style="text-decoration: underline;"&gt;P&lt;/span&gt;. &lt;span style="text-decoration: underline;"&gt;maxima&lt;/span&gt;) farming particularly in the Kapontori Bay, Buton Island waters and in other areas had complained for the mass mortality of pearl oysters saplings on the shell width between 3-4 cm. The mass mortality, was allegedly as a result of changing in environmental conditions and triggered by the shift in seasons. This research aimed to determine the effect of seasonal variations in water conditions at different depth levels on growth and survival of seedlings of pearl oysters conducted on March 27, 2007 to February 28, 2008. This research was very useful for pearl oyster farming in an effort to suppress the mass mortality rates based on the appropriate level of depth and seasons. The variance analyses showed that depth levels affected the survival rates of the pearl oyster seeds significantly (P&amp;lt;0.01). Based on honest significantly difference test, it also showed that the percentage number of survival rate was found higher within the depth of 2m (93.33%). Based on the relationship analyses between length and weight of shell body in all depths indicated a similar growth pattern of minor allometric (b&amp;lt;3). The growth, survival rate, and environmental conditions based on depth levels on pearl oyster saplings were discussed in this paper.&lt;/p&gt; &lt;p&gt;Keywords: Seasonal variation, survival rate, growth, pearl shell (&lt;span style="text-decoration: underline;"&gt;P&lt;/span&gt;. &lt;span style="text-decoration: underline;"&gt;maxima&lt;/span&gt;), depth level&lt;/p&gt;

The influence of pearl oyster farming on reef fish abundance and diversity in Ahe, French Polynesia

Many cultured pearl farms are located in areas of the Pacific that have thriving, highly diverse fish communities but the impacts of farming on these communities are poorly understood. We studied the effects of pearl oyster farming on shore fish abundance and diversity in the lagoon of Ahe, French Polynesia by adapting roving diver census methods to the coral reef bommies of the lagoon and compared 16 sites with high pearl farming impact to others with no direct impact. Pearl farming has a slightly positive effect on reef fish abundance (N) and no significant impact on fish diversity (H) or community composition. This is important when considering the ecological sustainability of pearl farming in French Polynesia and suggests that a potential synergy between pearl farms and marine conservation should be further explored.

Bioremediation Mariculture in Zanzibar, Tanzania: A Viability Assessment of Using Bath Sponge and Pearl Oyster Farms to Filter Highly Polluted Waters in the Zanzibar Channel

Bioremediation of polluted water off the coastline of the urban center of Zanzibar—Stone Town, Unguja—was assessed for implementation feasibility through bath sponge and pearl oyster mariculture. A vast research base of the city’s coastal area exists, including the pollution concentrations at various locations, the ramifications of this pollution on the fringing ecosystems, and the relevant water circulation system of eddies and passageways produced by the north flowing East African Counter Current. In following the experimental examples of bioremediation projects around the world, this study tested facets of the filtration abilities of marine sponges and oysters. Both organisms suggested strong pollution filtration abilities. Phosphate concentrations decreased from an average of 3.93 ug/L (micrograms per liter) to 1.33 and 1.73 ug/L for sponges and oysters, respectively. Unique capabilities of each organism were displayed in the experiments. The marine sponges visibly eliminated the turbidity level in the 36-hour study period. The marine oysters were suggested to chemically convert the dissolved nitrates through the tested increase in ammonium concentration from an average of 4.01 ug/L in the contaminated water to and average replicate concentration of 21.5 ug/L. The respective mariculture techniques were examined along with management logistics to assess the viability of implementing the mariculture for the pollution remediation. It was concluded that the mariculture techniques could be feasibly established by carefully collaborating with the nature of the pollution distribution, the consultation and aid of private and governmental organizations and further background scientific research.

Spatial and temporal dynamics of size-structured photosynthetic parameters (PAM) and primary production (13C) of pico- and nano-phytoplankton in an atoll lagoon

Atoll lagoons display a high diversity of trophic states due mainly to their specific geomorphology, and probably to their level and mode of human exploitation. We investigated the functioning of the Ahe atoll lagoon, utilized for pearl oyster farming, through estimations of photosynthetic parameters (pulse amplitude modulation fluorometry) and primary production (13C incorporation) measurements of the size structured phytoplankton biomass (<2μm and >2μm). Spatial and temporal scales of variability were surveyed during four seasons, over 16months, at four sites within the lagoon. While primary production (P) was dominated by the picophytoplankton, its biomass specific primary productivity (PB) was lower than in other atoll lagoons. The variables size fraction of the phytoplankton, water temperature, season, the interaction term station*fraction and site, explained significantly the variance of the data set using redundancy analysis. No significant trends over depth were observed in the range of 0–20m. A clear spatial pattern was found which was persistent over the seasons: south and north sites were different from the two central stations for most of the measured variables. This pattern could possibly be explained by the existence of water cells showing different water residence time within the lagoon. Photoacclimation strategies of the two size fractions differed through their light saturation coefficient (higher for picophytoplankton), but not through their maximum photosynthetic capacity (ETRmax). Positive linear relationships between photosynthetic parameters indicated that their dynamic was independent of light availability in this ecosystem, but most probably dependent on nutrient availability and/or rapid changes in the community structure. Spatial and temporal patterns of the measured processes are then further discussed in the context of nutrient availability and the possible role of cultured oysters in nutrient recycling.