Ecology of Blue-Green Algae in Aquaculture Ponds

Cyanobacteria (blue-green algae) in the genera Anabaena, Aphanizomenon, Microcystis, and Oscillatoria often form extensive and persistent blooms in freshwater aquaculture ponds. Bloom-forming cyanobacteria are undesirable in aquaculture ponds because: 1) they are a relatively poor base for aquatic food chains; 2) they are poor oxygenators of the water and have undesirable growth habits; 3) some species produce odorous metabolites that impart undesirable flavors to the cultured animal; and 4) some species may produce compounds that are toxic to aquatic animals. Development of cyanobacterial blooms is favored under conditions of high nutrient loading rates (particularly if the availability of nitrogen is limited relative to phosphorus), low rates of vertical mixing, and warm water temperatures. Under those conditions, dominance of phytoplankton communities by cyanobacteria is the result of certain unique physiological attributes (in particular, N₂ fixation and buoyancy regulation) that allow cyanobacteria to compete effectively with other phytoplankton. The ability to fix N₂ provides a competitive advantage under severe nitrogen limitation because it allows certain cyanobacterial species to make use of a source of nitrogen unavailable to other phytoplankton. The ability to regulate cell buoyancy through environmentally-controlled collapse ad reformation of intracellular gas vacuoles is perhaps the primary reason for the frequent dominance of aquaculture pond phytoplankton communities by cyanobacteria. Cyanobacteria that can regulate their position in the water column gain a distinct advantage over other phototrophs in poorly mixed bodies of water. In addition to the physicochemical interactions that influence phytoplankton community dynamics, cyanobacterial-microbial associations may play an important regulatory role in determining community structure. Cyanobacteria are always found in close association with a diverse array of microorganisms, including eubacteria, fungi, and protozoans. These associations, which in the past have often been viewed as antagonistic, are increasingly seen as mutualistic and may function in a positive manner during bloom development.     

Haematological indices are modulated in juvenile carp, Cyprinus carpio L., exposed to microcystins produced by cyanobacterial water bloom

This study evaluated the influence of toxic cyanobacterial water blooms on the blood indices of the common carp, Cyprinus carpio L. Experimental fish were exposed to a natural population of cyanobacterial water blooms (mainly Microcystis aeruginosa and M. ichthyoblabe), which contained microcystins [total concentration 133–284 μg g^?1 (DW), concentration in water 2.8–7.4 μg L^?1]. Haematological indices showed marked changes in fish exposed to the cyanobacterial population in comparison with the control group. Statistical evaluation of the influence of cyanobacterial water blooms on biochemical indices of the juvenile carp showed a distinct decrease in albumin, alanine aminotransferase, total bilirubin, calcium, cholesterol, glucose, phosphorus and iron when compared to controls. Values of red blood counts [haemoglobin, haematocrit (PCV), mean corpuscular haemoglobin and mean corpuscular haemoglobin concentration] and lactate were significantly increased compared to controls. After exposure to cyanobacterial water bloom, the carp were kept in clean water to monitor the persistence of biochemical indices. The influence of cyanobacterial populations on calcium, cholesterol, glucose, lactate, phosphorus and PCV persisted up to 28 days after conclusion of the experiment. Duration of exposure, toxicity and density of cyanobacterial water blooms had an important impact on individual haematological indices.     

A review of cyanobacterial odorous and bioactive metabolites: Impacts and management alternatives in aquaculture

Increased demand has pushed extensive aquaculture towards intensively operated production systems, commonly resulting in eutrophic conditions and cyanobacterial blooms. This review summarizes those cyanobacterial secondary metabolites that can cause undesirable tastes and odors (odorous metabolites) or are biochemically active (bioactive metabolites) in marine and freshwater, extensive and intensive aquaculture systems. For the scope of this paper, biochemically active metabolites include (1) toxins that can cause mortality in aquaculture organisms or have the potential to harm consumers via accumulation in the product (hepatotoxins, cytotoxins, neurotoxins, dermatoxins, and brine shrimp/molluskal toxins), (2) metabolites that may degrade the nutritional status of aquaculture species (inhibitors of proteases and grazer deterrents) or (3) metabolites that have the potential to negatively affect the general health of aquaculture species or aquaculture laborers (dermatoxins, irritant toxins, hepatotoxins, cytotoxins). Suggestions are made as to future management practices in intensive and extensive aquaculture and the potential exposure pathways to aquaculture species and human consumers are identified.     

Controlling the growth of a cyanobacterial contaminant, Synechoccus sp., in a culture of Tetraselmis chui (PLY429) by varying pH: Implications for outdoor aquaculture production

In aquaculture, large volumes of phytoplankton are often grown outdoors to reduce costs. However, growing microalgae in an environment not as well-controlled as in the laboratory can lead to unwanted phytoplankton, including cyanobacteria, contaminating a culture. A cyanobacterial contaminant was isolated from an outdoor culture of Tetraselmis chui (PLY429) at the Milford Laboratory. This study investigated the growth of PLY429 and the cyanobacterium in pure cultures and a mixed culture in a pH range of 6.5-9.5. The division of PLY429 was greater at a pH range of 7.0-8.0; whereas, for the cyanobacterium, higher growth was obtained at pH 8.0-9.0. Results from combined cultures of PLY429 and the cyanobacterium grown at various pHs indicated that maintaining pH near 7.1 yields higher growth of PLY429 than those of the cyanobacterium. These findings suggest that controlling pH may reduce the population of a cyanobacterial contaminant in an aquaculture feed culture.     

The dynamics of bacterial community in a polyculture aquaculture system of Penaeus chinensis,Rhopilema esculenta and Sinonovacula constricta

Polyculture with Chinese shrimp Penaeus chinensis, jellyfish Rhopilema esculenta and razor clam Sinonovacula constricta (S.J.R) is a common aquaculture system in Dandong, China. Investigation on the composition and function of microbial communities and their relationship with environmental factors in aquaculture systems have crucial implications. Therefore, the sequencing of 16S rRNA gene was applied to profile the bacterial community composition of water and sediment in S.J.R polyculture system in the present study. Proteobacteria was the dominant phylum in S.J.R polyculture ponds following with Actinobacteria and Bacteroidetes in water; in contrast, more diverse phyla were detected in sediments. Water temperature, pH and dissolved oxygen were determined the bacterial community composition in the S.J.R polyculture systems. Specially, Planktomarina, PS1 clade, Candidatus Aquiluna and Fibrobacteres, which can resist the phytoplankton blooms or degrade the cellulose, were more abundant in water at the early stage of cultivation in the S.J.R polyculture system. Moreover, the functions of bacterial communities in water were mainly associated with cell communication mediated, while the functions related to basal metabolism were enriched in sediments. The findings of this study allowed us to better understand the bacterial community in the S.J.R polyculture system and accumulated data for the improvement of cultural management.     

富藻养殖水体中金鱼藻和篦齿眼子菜的抑藻效果研究

夏季高温时,养殖水体水华现象频繁发生,给养殖业带来巨大的损失。常见水生植物释放的活性物质在低浓度下可以起到抑藻作用,对藻类调控具有重要意义。本研究采用实验室静态模拟方法,取养殖池塘暴发蓝藻水华的水体,与沉水植物金鱼藻(Ceratophyllum demersum)及篦齿眼子菜(Potamogeton pectinatus)进行共培养,研究这2种沉水植物对养殖水华水体营养水平、藻类生长、藻类结构及浮游藻类生物多样性的影响。结果显示,金鱼藻和篦齿眼子菜可显著降低水华水体氮、磷等营养水平(P<0.05);金鱼藻和篦齿眼子菜可有效抑制水华蓝藻(Cyanobacteria)生长,尤其对颤藻和微囊藻(Microcystis sp.)效果显著(P<0.05),且篦齿眼子菜对水华蓝藻抑制效果更为显著。实验结束时,篦齿眼子菜培养组藻密度下降93.6%,生物量下降98.9%,叶绿素a含量下降60.5%;金鱼藻培养组藻密度下降72.5%,生物量下降86.8%,叶绿素a含量下降54.3%;金鱼藻和篦齿眼子菜的存在可促进养殖水体浮游藻类生物多样性增加,且金鱼藻提高浮游藻类生物多样性效果更显著。金鱼藻培养组浮游藻类生物多样性升高98.4%,篦齿眼子菜培养组浮游藻类生物多样性升高50.3%。本研究结果可为未来生态养殖提供理论依据和参考。     

Quantifying Aquaculture‐derived Dissolved Organic Matter in the Mesocosms of Sanggou Bay Using Excitation‐emission Matrix Spectra and Parallel Factor Analysis

The cycling and fate of dissolved organic matter (DOM) in aquaculture systems are unique. Sanggou Bay, an aquaculture‐dominated system in China, was chosen to characterize the composition of DOM based on optical properties. Field incubation experiments of eight mesocosms containing various aquaculture organisms were conducted in July 2013 to explore the impact of aquaculture organisms on the DOM composition. Dissolved organic carbon (DOC) showed an increasing trend, especially in integrated mesocosms, suggesting the accumulation of DOM in the aquaculture ecosystem. The DOC concentration was positively correlated with a₂₈₀ (P < 0.01) rather than a₃₅₅, demonstrating that a₂₈₀ should be applied in the quantitative prediction of DOC in aquaculture systems. Parallel factor analysis was applied to identify the components of the excitation‐emission matrix spectra. Two humic‐like components and two protein‐like components were identified. The significant correlation between the wet weights of the organisms and the humic‐like component contents (P < 0.01) indicated that seaweeds and bivalves play important roles in the production of humic‐like matter. The variation of protein‐like materials was caused by the growth of aquaculture organisms and the decay of phytoplankton. The amount of bioavailable DOC (BDOC) derived from phytoplankton and organisms was estimated; bivalve organisms excreted more BDOC than did seaweeds. BDOC was significantly correlated with the protein‐like components (P < 0.05) in the microbial incubation experiment.     

Photosynthetic suspended-growth systems in aquaculture

Standardized evaluation and rating of biofilters for aquaculture should be assessed in the context of the economic efficiency of ecological services (waste assimilation, nutrient recycling, and internal food production) provided by earthen ponds, and the availability and cost of land, water, and electrical energy resources required to support particular classes of production systems. In photosynthetic suspended-growth systems, water quality control is achieved by a combination of natural and mechanical processes. Natural processes include photosynthesis of oxygen, algal nutrient uptake, coupled nitrification–denitrification, and organic matter oxidation; mechanical processes include aeration and water circulation. Ammonia is controlled by a combination of phytoplankton uptake, nitrification, and immobilization by bacteria. Unlike biofilters for recirculating aquaculture systems, unit processes are combined and are an integral part of the culture unit. The important design and operational considerations for photosynthetic suspended-growth systems include temperature effects, aeration and mixing, quantity and quality of loaded organic matter, and fish water quality tolerance limits. The principle advantages of photosynthetic suspended-growth systems are lower capital costs relative to other recirculating aquaculture systems and increased control over stock management relative to conventional static ponds. The main disadvantage is the relatively low degree of control over water quality and phytoplankton density, metabolism, and community composition relative to other recirculating aquaculture systems. Examples of photosynthetic suspended-growth systems include semi-intensive ponds, intensively aerated outdoor lined ponds, combined intensive–extensive ponds, partitioned aquaculture systems, greenwater tanks, greenwater tanks with solids removal, and greenwater recirculating aquaculture systems.     

东莞市25座水库的营养现状与水质管理对策

为了解东莞市水库富营养化现状并为水质管理提出合理建议,于2011-2012年的丰水期、平水期和枯水期,对东莞市25座水库的营养状态和浮游植物主要参数进行分析。结果显示,中营养水库5座,富营养水库16座,超富营养水库4座,整体富营养化水平较高。水库浮游植物丰度1.07×105~7.67×108个/L,且枯水期高于丰水期;有20座水库的浮游植物丰度中蓝藻比例超过50%,部分水库出现了蓝藻水华现象,其营养状态与人类活动强度、流域内土地利用类型、水库功能及补水方式密切相关。削减外源污染,尤其是控制磷排放是当前遏制水库富营养化的根本途径;对于即将联网调水的5座水库而言,利用联网形成的调度能力进行合理的水库调度是缓解其富营养化的可行措施。     

The timing of inorganic fertilization of sunfish ponds

Fertilization with diammonium phosphate (20 kg/ha per application) was initiated at different dates in each of four treatments replicated three times in 0.04-ha ponds. Although there were some differences in averages of total and filtrable orthophosphate concentrations and phytoplankton abundance among treatments (P < 0.05), sunfish production was not influenced by the timing of fertilization (P > 0.05). Phytoplankton blooms did not develop in any of the treatments until late spring or early summer. The failure of phytoplankton to respond to fertilization in late winter and early spring was apparently related to low water temperature and competition by macrophytes. In larger, deeper ponds (> 0.5 ha), inorganic fertilization will cause phytoplankton blooms in early spring even when water temperatures are low.     

Assessing Noxious Phytoplankton in Aquaculture Systems Using Bio-Optical Methodologies: A Review

Management practices in aquaculture systems contribute to maximum growth of phytoplankton, often resulting in extensive blooms of noxious cyanobacteria. Because periods of oxygen depletion and “off flavor” events correspond to intense algal growth and metabolic activity, accurate identification of algal dynamics and physiological state is important. Current efforts to assess algal assemblages rely upon microscopic evaluation; however, the incorporation of such evaluation into monitoring programs is limited due to the level of skill and training required, the excessive costs and time required to assess algal heterogeneity within/among aquaculture systems, and the lack of information provided concerning physiological state. The distinct biwptical characteristics of the blooms lend themselves to pigment-based methodologies (pigment and in vivo absorption “signatures”, chlorophyll a fluorescence, multi-spectral remote sensing) which complement microscopic evaluation and can be implemented into large-scale monitoring programs. For example, because the key ingredient for success of such programs is the rapid, reliable, and accurate characterization of algal biomass along variable temporal/spatial scales, remotely-sensed data acquisition most likely will be required. High-performance liquid chromatography (HPLC)-derived pigment and in vivo absorption “signatures” can delineate problematic algal phylogenetic groups and physiological states. Further, measurements of chlorophyll a fluorescence provide estimates of phytoplankton absorption, quantum efficiency, and potentially production potential and growth rate. As such, they can be used to confirm the systematic significance of remotely-sensed data. It would be highly desirable to integrate an evaluation program using bio-optical methodologies into a geographic information system to allow for integrating, modeling, and predicting parameters of management interest over the scales relevant to aquacultural and water resource management.     

Phytoplankton community structure and diversity in the indoor industrial aquaculture system for Litopenaeus vannamei revealed by high‐throughput sequencing and morphological identification

The explosive multiplication of phytoplankton caused by water eutrophication often occur in the intensive shrimp aquaculture. To comprehensively assess the diversity and community structure of phytoplankton in the waters of typical indoor industrial aquaculture system for Litopenaeus vannamei, a combination of high‐throughput sequencing and morphological identification methods were used in the present study. A total of 41 genera belong to nine phyla were detected by both methods. Chlorophyta, Cyanophyta and Bacillariophyta were found to be three dominant phyla. The high‐throughput sequencing revealed that green algae and cyanobacteria were the most dominant phytoplankton; however, diatoms were the first dominant phytoplankton by using the morphological identification. At the genus level, Picochlorum and Synechococcus were dominant, accounting for 20.94%–97.19% and 0.01%–52.81% of total phytoplankton, revealed by the high‐throughput sequencing. Therefore, more attention should be paid to their ecological impacts on the surrounding sea areas or potential toxicity to shrimp. Cyclotella was the most dominant genus revealed by the morphological identification. High‐throughput sequencing revealed a high diversity and small‐sized phytoplankton which were undetected by microscopy. Both methods provide similar information on the environmental drivers of phytoplankton community. NO₃^?, NH₄⁺, DIP, DSi, DON and DOP concentrations were the main factors influencing the phytoplankton community structure and diversity.     

Impact of short‐term climate effects and sea ice coverage variation on Japanese scallop aquaculture in Saroma Lake,Japan

Saroma Lake is the southernmost lagoon exhibiting seasonal sea ice coverage in the Northern hemisphere and one of the most important aquaculture areas for Japanese scallops (Mizuhopecten yessoensis). Under conditions of adequate food and appropriate temperature, scallops grow well from the time of ice melting in April to harvesting starting in July. However, over the past decade, Saroma Lake frequently has not been completely covered by ice in winter, and the production of Japanese scallops has shown significant changes. Therefore, this study integrated data from satellite remote sensing, buoys, and in situ observations with climatic events [the winter East Asian Monsoon (EAM) and El Niño/La Niña–Southern Oscillation events] to investigate the impact of ice coverage variations on scallop growth in Saroma Lake between 2007 and 2015. Daily ice conditions were detected using Moderate Resolution Imaging Spectroradiometer false colour images and an unsupervised classification method. The results indicated that EAM strongly influenced the ice coverage variation in Saroma Lake through their effects on temperature during winter. Ice coverage variations show a strong correlation with water temperature and spring phytoplankton blooms, which are the two most important environmental factors for scallop growth. In addition, extreme climate events could cause water temperature anomalies (as in 2015) which are unfavourable for scallop growth. Monitoring ice conditions should be considered when developing plans and management strategies for scallop aquaculture in Saroma Lake.     

蓝藻水华及其次生危害

本文简要介绍了蓝藻水华、蓝藻的次生代谢产物——微囊藻毒素以及与此有关的重大事件。微囊藻毒素是一种小分子的环肽化合物,能损害脊椎动物的肝、肾、性腺、神经、心脏等器官,是一类毒性很强的生物毒素,尤其对哺乳动物的毒性很强,是饮用水源安全保护的一项重大挑战。因此,建立由政府、企业和科学家的合作模式,集流域污染源控制、生态修复(保育)与可持续渔业为一体,通过维持水域生态系统代谢机制的良性过程,达到保护水质的目的,是未来的一个重要发展方向。     

过氧化钙对武汉东湖浮游植物群落及水环境的影响

为探讨过氧化钙作为化学除藻剂对浮游植物群落和水质的影响,于2020年10月采集武汉东湖原水,在深度为2m的水柱中使用不同剂量的过氧化钙进行处理。结果显示：40 mg/L、60 mg/L、80 mg/L的过氧化钙在东湖原水中释放的过氧化氢最高浓度分别为17.04±0.82mg/L、22.21±0.81 mg/L和31.67±2.47mg/L;水柱0~1.0 m水层的过氧化氢含量显著高于1.0-2.0m水层,持续释放时间可达36h~48h;过氧化钙的使用能显著减少底层水体的正磷酸盐含量;同时,过氧化钙在处理12h后可显著降低水柱中叶绿素 a含量和蓝藻的相对丰度（P<0.05）,同时提高了绿藻相对丰度28.06%,将硅藻相对丰度提高了27.25%,改变浮游植物群落的物种优势度,具有选择性杀灭蓝藻的效果。本研究可为过氧化钙在蓝藻水华处置、水体富营养化治理等方面的应用提供参考依据。     

Comparative Nile tilapia and silver carp filtration rates of Partitioned Aquaculture System phytoplankton

Nile tilapia (Oreochromis niloticus) and silver carp (Hypophthalmichthys molitrix) held in timed-pulse feeding chambers were provided water dominated either by green algae (Scenedesmus, Ankistrodesmus and Tetraedron) or by cyanobacteria (Microcystis) to compare filtration rates (FRs). FRs were expressed as suspended particulate organic carbon (POC)/kg wet fish weight/h and as phytoplankton units filtered based on counts. Nile tilapia and silver carp filtration significantly reduced phytoplankton number of both taxonomic groups with the larger phytoplankton being filtered proportionally more than the smaller phytoplankton. Nile tilapia FR of green algae was significantly higher than silver carp; however, silver carp FR of cyanobacteria was higher than Nile tilapia. Ivlev's 90% saturation FRs (FR₉₀) in green-algal and cyanobacterial water sources were 702 and 812 mgC/kg/h for Nile tilapia and 414 and 1028 mgC/kg/h for silver carp, respectively. Silver carp were observed to reach these FR₉₀ values at lower POC concentrations than Nile tilapia with both green algae and cyanobacteria.     

Wetland creation: early stages in colonization of phytoplankton and submerged macrophytes in hypereutrophic freshwater lagoons

1. Colonization by macrophyte and phytoplankton communities was recorded in the newly created freshwater wetland complex at the Wildfowl and Wetlands Trust (WWT), The Wetlands Centre, London. To attract particular bird species and to increase overall invertebrate and vertebrate biodiversity it was originally planned to establish a number of different submerged aquatic macrophyte communities in the water bodies. Early planting schemes were abandoned due to extensive growths of filamentous macroalgae. 2. During 1997 and 1998 hypereutrophic conditions prevailed in the lagoons with peak concentrations of total phosphorus (TP) in excess of 1000 mg m⁻³. Turbidity was high and dense algal crops and cyanobacterial blooms common, with chlorophyll a concentrations in excess of 40 mg m⁻³. 3. In 1999, a ‘switch’ in state occurred in the Sheltered Lagoon from a turbid lake dominated by cyanobacteria and filamentous macroalgae in 1998, to a clear lake, dominated by the macrophyte Myriophyllum spicatum L. with a mean biomass of 245 g dry weight m⁻²; concentrations of TP remained high (>200 mg m⁻³). 4. Possible causes for the switch in the Sheltered Lagoon are considered. Reduction in TP was not considered to be sufficient to trigger a switch. The smaller size (1.8 ha), with smaller fetch and greater protection from wind mixing may have reduced sediment suspension in the Sheltered Lagoon and, coupled with water level changes, may have created favourable light conditions for the establishment of M. spicatum. Implications for future design and management of the water bodies are considered. Copyright © 2000 John Wiley & Sons, Ltd.     

The use of model ponds to evaluate phytoplankton blooms and benthic algal mats for Penaeus monodon Fabricius culture

Abstract. Fibreglass pools (3·5m diameter, 1·2m high) were evaluated as model ponds and used to compare the effects of fertilization strategies, designed to promote either phytoplankton blooms or benthic algal mats, on production of Penaeus monodon Fabricius and water quality over 8 weeks. As production results were similar to those reported from commercial ponds in Australia and Taiwan, the pools were considered appropriate experimental units for assessing pond management strategies. Large blooms of filamentous algae developed in four of the eight pools with benthic algae. In these, individual prawn growth (weight gain), biomass gain, food conversion efficiency and drain harvest efficiency were all lower ( P < 0·05) than in pools with phytoplankton. Abundance of filamentous algae was negatively correlated ( P < 0·05) with prawn weight gain (r =−0·80) and drain harvest efficiency (r =−0·76). Differences in water quality arising from alternative fertilization strategies occurred but did not explain differences in prawn production indices. The results indicate that ponds used for monoculture of P. monodon should be fertilized so as to stimulate and maintain phytoplankton blooms and to discourage blooms of filamentous algae.     

Plankton dynamics: observed and modelled responses to physical conditions in Prince William Sound,Alaska

Plankton populations in Prince William Sound, Alaska, exhibited pronounced seasonal, annual and longer‐period variability in composition and standing stock in response to physically influenced differences in nutrient availability, and possibly currents that modify local biomass by exchanges with water from the bordering Gulf of Alaska. During springs in which early, strong physical stratification developed, intense, short‐lived phytoplankton blooms occurred. These blooms had relatively short residence times in the water column. In contrast, during springs in which slower, weaker stratification developed, phytoplankton blooms were prolonged and took longer to peak. These slower blooms prolonged the period of phytoplankton production, prolonged interaction with the springtime grazing community and led to the incorporation of more organic matter into pelagic food webs. A coupled biological‐physical simulation of plankton production was used to examine the implications of seasonally varying air and mixed‐layer temperatures, surface winds and incident light on the timing, duration, annual production and standing stock of plankton. Our modelling results reproduced the observed characteristics of the springtime production cycle, and the magnitude of zooplankton stocks for the period 1992–97 but not for 1981–91. These results suggest that for most of the 1990s, bottom‐up influences on nutrient supplies controlled levels of primary consumers, whereas for the 11 years before that, other unknown factors dominated this process. We present the results of a comprehensive, multiyear study of relationships between plankton and physical limitations, and a retrospective analysis of earlier conditions to explore the possible causes for these differences.     

菲律宾蛤仔垦区育苗技术优化及其对池塘理化环境、浮游植物和稚贝生长的影响

为改进菲律宾蛤仔垦区育苗技术,设置一口池塘(A)培育高密度浮游植物并定期添加至育苗池(B),未添加藻类育苗池(C)作为对照,比较了A、B、C以及邻近自然海区(D)的水体、沉积物、浮游植物状况和池塘B、C中稚贝生长情况。结果显示,池塘A、B、C之间水质和沉积物各指标无显著性差异,但三者水体中盐度、pH、溶解氧、氨氮、硝酸盐氮、活性磷酸盐和沉积物中有机碳、硫化物与自然海区D差异显著;浮游植物密度ABCD,但仅A、D间差异显著;池塘B稚贝壳长和密度均显著大于池塘C。这表明垦区与自然海区环境差异大,而育苗期间通过外源补充藻类能提高稚贝的生长率和成活率,进而提高菲律宾蛤仔垦区育苗成功率。