Sea Aquaculture Research Articles

Spatiotemporal Dynamics and Drivers of Coastal Wetlands in Tianjin–Hebei over the Past 80 Years

Coastal wetland ecosystems are critical due to their diverse ecological and economic benefits, yet they have been significantly affected by human activities over the past century. Understanding the spatiotemporal changes and underlying factors influencing these ecosystems is crucial for developing effective ecological protection and restoration strategies. This study examines the Tianjin–Hebei coastal wetlands using topographic maps from the 1940s and Landsat satellite imagery from 1975, 2000, and 2020, supplemented by historical literature and field surveys. The aim is to analyze the distribution and classification of coastal wetlands across various temporal intervals. The findings indicate an expansion of the Tianjin–Hebei coastal wetlands from 7301.34 km2 in the 1940s to 8041.73 km2 in 2020. However, natural wetlands have declined by approximately 44.36 km2/year, while constructed wetlands have increased by around 53.61 km2/year. The wetlands have also become increasingly fragmented, with higher numbers of patches and densities. The analysis of driving factors points to human activities—such as urban construction, cultivated land reclamation, sea aquaculture, and land reclamation—as the primary contributors to these changes. Furthermore, the study addresses the ecological and environmental issues stemming from wetland changes and proposes strategies for wetland conservation. This research aims to enhance the understanding among researchers and policymakers of the dynamics and drivers of coastal wetland changes, as well as the major challenges in their protection, and to serve as a foundation for developing evidence-based conservation and restoration strategies.

Development of a haplotype reference panel and analysis of genetic structure in Golden Pompano (Trachinotus ovatus)

Trachinotus ovatus, a valuable marine fish, is primarily farmed in the South China Sea. Intensive aquaculture can lead to genetic uniformity and disease risks. Additionally, the high cost of genome sequencing restricts knowledge of genetic variation, hindering genetic analysis and breeding advancements. This study investigated the genetic diversity and structure of Trachinotus ovatus populations within the South China Sea aquaculture context, with the goal of strengthening sustainability. Additionally, the study also enhanced breeding strategies by developing a high-quality haplotype reference panel and an efficient imputation process. Through high-throughput sequencing (depth＞20X), 173 samples from three key breeding sites (SanYa, Hainan; Zhanjiang, Guangdong; and Beihai, Guangxi) were analyzed, revealing substantial genetic diversity and distinct population structures. Notably, the Beihai (BH) population exhibited significant stratification, suggesting regional genetic uniqueness. Low levels of genomic inbreeding coefficient and the identification of unique SNP loci across populations underscored the genetic richness within these Trachinotus ovatus communities. A major constructed of this work is the creation of the first high-quality haplotype reference panel for the species, demonstrating genotype imputation's viability as a cost-effective alternative for large-scale genetic studies in aquaculture. In particular, a Shapeit reference panel with 5476,550 SNPs was created, excelling in accuracy across various depths, notably achieving up to 95.8 % imputation accuracy at 1X sequencing depth. This high accuracy across populations shows the importance of genetic diversity in the panel. This research not only advances the understanding of Trachinotus ovatus genetic foundations but also provides crucial insights for conservation efforts and genetic analysis. By establishing a robust haplotype reference panel for Trachinotus ovatus helps lower the costs of future genetic research and variation studies, this study lays the foundation for sustainable aquaculture practices and breeding programs.

Comparison of ovarian mRNA expression levels in wild and hatchery-produced greater amberjack Seriola dumerili

The greater amberjack Seriola dumerili is a promising candidate for aquaculture production. This study compares the ovary transcriptome of greater amberjack sampled in the wild (WILD) with hatchery-produced breeders reared in aquaculture sea cages in the Mediterranean Sea. Among the seven sampled cultured fish, three were classified as reproductively dysfunctional (DysF group), while four showed no signs of reproductive alteration (NormalF group). The DysF fish showed 1,166 differentially expressed genes (DEGs) compared to WILD females, and 755 DEGs compared to the NormalF. According to gene ontology (GO) analysis, DysF females exhibited enrichment of genes belonging to the biological categories classified as Secreted, ECM-receptor interaction, and Focal adhesion. Protein–protein interaction analysis revealed proteins involved in the biological categories of ECM-receptor interaction, Enzyme-linked receptor protein signaling, Wnt signal transduction pathways, and Ovulation cycle. KEGG pathway analysis showed DEGs involved in 111 pathways, including Neuroactive ligand-receptor interaction, Steroid hormone biosynthesis, Cell cycle, Oocyte meiosis, Necroptosis, Ferroptosis, Apoptosis, Autophagy, Progesterone-mediated oocyte maturation, Endocytosis and Phagosome, as well as Hedgehog, Apelin, PPAR, Notch, and GnRH signalling pathways. Additionally, DysF females exhibited factors encoded by upregulated genes associated with hypogonadism and polycystic ovary syndrome in mammals. This study -which is part of a broader research effort examining the transcriptome of the entire reproductive axis in greater amberjack of both sexes-, enhances our comprehension of the mechanisms underlying the appearance of reproductive dysfunctions when fish are reared under aquaculture conditions.

Rotation Culture of Macroalgae Based on Photosynthetic Physiological Characteristics of Algae

Seaweed farming has made outstanding contributions to food supply and the restoration of the ecological environment despite the limitations in production and ecological effects due to the current intensive farming of single algae species. These limitations can be overcome by selecting suitable algal species based on their physiological characteristics and by constructing a large-scale seaweed rotation model. This study carried out a trial culture in aquaculture sea areas, and performed in situ monitoring of the environmental conditions and physiological characteristics of Saccharina japonica, Hizikia fusiformis, and Gracilariopsis lemaneiformis. Additionally, a comparative analysis of the three macroalgae at different times was conducted to determine their response characteristics to environmental factors. The results showed that: (1) The three macroalgae had varying light tolerance. The effective quantum yield of Hizikia fusiformis and Gracilariopsis lemaneiformis remained unchanged during the changes in light environment, while that of Saccharina japonica first decreased and then recovered. (2) The relative electron transport rates of the three macroalgae were significantly different under different temperature conditions. Hizikia fusiformis and Saccharina japonica exhibited the highest relative electron transport rates (70.45 and 106.75, respectively) in May (20.3 °C). Notably, Gracilariopsis lemaneiformis demonstrated good growth and exhibited the highest relative electron transport rate (93.07) in September (27.5 °C). These findings collectively support the feasibility of establishing a macroalgae rotation model. Based on the combined environmental conditions of the seas in Shandong, Zhejiang, and Fujian, a macroalgae rotation model was proposed. The application of this model in the construction of artificial seaweed farms in marine ranches can provide a stable output of large-scale seaweed production and ecological benefits.

The Effect of Marine Pastures on Green Aquaculture in China

Under the double pressures of economic growth and ecological environment protection, sea green transformation and the sustainable development of mariculture are critical. This paper constructs an evolutionary game model with the government as the main body and mariculture farmers (enterprises) as the main body and puts forward the research hypothesis. Based on 2006–2019 longitudinal data of nine provinces along China’s coast, using multi-period Difference-in-Difference (DID) and dual robust estimation, we empirically investigate the national oceanic ranch demonstration zones for the influence of the green sea aquaculture and their mechanism of action. The results showed that (1) the efficiency of green level of mariculture industry in China is not high, and the establishment of national marine pasture demonstration zone has not effectively promoted the improvement of green level of mariculture industry; (2) the institutional environment, unreasonable industrial structure, and lack of scientific and technological innovation have an effect on the national oceanic ranch demonstration area as the main causes of failure to effectively promote marine green farming; (3) the establishment of the national multi-period demonstration area in the north significantly hindered the growth of the green level of mariculture and fell into the “policy trap”, while the establishment of the national multi-period demonstration area in the south significantly promoted the growth of the green level of mariculture. The conclusions of this paper provide an empirical basis and reference for the improvement of the national marine pasture demonstration zone policy and the green transformation of mariculture to a certain extent.

Model of Oxygen Conditions within Aquaculture Sea Cages.

To ensure optimal feed intake, growth, and general fish health in aquaculture sea cages, interactions between drivers that affect oxygen conditions need to be understood. The main drivers are oxygen consumption and water exchange, caused by flow through the cage. Swimming energetics in rainbow trout (Oncorhynchus mykiss) in normoxia and hypoxia at 10, 15, and 20 °C were determined. Using the determinations, a conceptual model of oxygen conditions within sea cages was created. By applying the model to a case study, results show that with a temperature increase of 10 °C, oxygen concentration will decrease three times faster. To maintain optimal oxygen concentration within the cage, the flow velocity must be increased by a factor of 3.7. The model is highly relevant for current farms since the model predictions can explain why and when suboptimal conditions occur within the cages. Using the same method, the model can be used to estimate the suitability of potential new aquaculture sites.

Automatic Extraction Method of Aquaculture Sea Based on Improved SegNet Model

Timely, accurate, and efficient extraction of aquaculture sea is important for the scientific and rational utilization of marine resources and protection of the marine environment. To improve the classification accuracy of remote sensing of aquaculture seas, this study proposes an automatic extraction method for aquaculture seas based on the improved SegNet model. This method adds a pyramid convolution module and a convolutional block attention module based on the SegNet network model, which can effectively increase the utilization ability of features and capture more global image information. Taking the Gaofen-1D image as an example, the effectiveness of the improved method was proven through ablation experiments on the two modules. The prediction results of the proposed method were compared with those of the U-Net, SegNet, and DenseNet models, as well as with those of the traditional support vector machine and random forest methods. The results showed that the improved model has a stronger generalization ability and higher extraction accuracy. The overall accuracy, mean intersection over union, and F1 score of the three test areas were 94.86%, 87.23%, and 96.59%, respectively. The accuracy of the method is significantly higher than those of the other methods, which proves the effectiveness of the method for the extraction of aquaculture seas and provides new technical support for automatic extraction of such areas.

U-YOLOv7: A network for underwater organism detection

Detecting and monitoring underwater organisms is very important for sea aquaculture. The human eye struggles to quickly distinguish between aquatic species due to their variety and dense dispersion. In this paper, a deep learning object detection algorithm based on YOLOv7 is used to design a new network, called Underwater-YOLOv7 (U-YOLOv7), for underwater organism detection. This model satisfies the requirements with regards to both speed and accuracy. First, a network combining CrossConv and an efficient squeeze-excitation module is created. This network increases the extraction of channel information while reducing parameters and enhancing the feature fusion of the network. Second, a lightweight Content-Aware ReAssembly of FEatures (CARAFE) operator is used to obtain more semantic information about underwater images before feature fusion. A 3D attention mechanism is incorporated to improve the anti-interference ability of the model in underwater recognition. Finally, a decoupling head using hybrid convolution is designed to accelerate convergence and improve the accuracy of underwater detection. The results show that the network proposed in this paper obtains an improvement of 3.2% in accuracy, 2.3% in recall, and 2.8% in the mean average precision value and runs at up to 179 fps, far outperforming other advanced networks. Moreover, it has a higher estimation accuracy than the YOLOv7 network.

High above the mountains, far across the sea—Aquaculture is helping to eradicate poverty in one of the world's most remote areas

The data that support the findings of this study are available from the corresponding author upon reasonable request.

The Hydrostatic Buckling of SPM Systems of Fish Cages and a Design Method to Prevent It

This study presents an inherent buckling issue of SPM (Single Point Mooring) systems for open sea aquaculture and a design method to analyze and solve this issue. The SPM arrangement of a row of cages is very efficient, as it minimizes the anchoring load by masking of the current applied to the downstream cages, hence saves anchors and mooring lines. However, a sudden reversal of the current direction presents a risk of buckling of the row of cages, if it applies a compression load along the array of cages before rotation of the entire cage system takes place. This study presents the concept of Hydrostatic Buckling of a row of cages and a method of design and analysis to control the stability of the system at the situation of sudden current reversal. First, a simple method for preliminarily assessment by applying the principle of virtual work is formulated. Then, an analysis of the structure by a parametric finite elements code is presented. The reversal current limits for the stability of the structure, are parametrically studied, by the analyses of two hypothetical practical scenarios. This study presents practical design tools and results, such as the method of the analysis, simplified loading states for representing the critical events, the scantlings of the structure, as well as guidelines for designing a SPM system of cages that withstand critical situations of reversal current.

Fostering the Development of Western Black Sea Aquaculture: A Scientific Case Study for Finfish Cage Farming Allocated Zone Designation

Mariculture offers enormous potential for providing sustainable food, playing a key role in achieving nutrition security, employment, and Blue Growth. This is particularly true in geographical areas where the dependence of local economies on fishery products is high and yet access to sustainable landings is hindered by environmental drawbacks. One such area is represented by the Black Sea, which offers different degrees of suitability for aquaculture development. While the southern and eastern shores are sheltered enough to allow for the development of large aquaculture activities, the north-western shoreline is characterized by wide environmental fluctuations and the strong influence of the Danube. This study aimed at investigating the suitability of a selected area of the Romanian coast (Mangalia) for finfish cage farming by adapting an internationally endorsed methodology for determining its Degree of Compatibility (DC). The development and expansion of finfish aquaculture depends on the availability of space, so designating Allocated Zones for Aquaculture (AZAs) is essential. The result obtained (DC = 80) indicates that the Mangalia area is suitable for finfish aquaculture activities: there is no major interference with other uses of the maritime space, no conflicts with nature conservation, and the environmental conditions are appropriate for fish culture in floating cages. The novel information provided by this study can be the building block for authorities to settle the governance gap that has so far impeded the development of marine aquaculture in Romania. At a larger scale, this study can serve as a good practice example at the regional Black Sea level.

Antiparasitic effect of copper alloy mesh on tomont stage of Cryptocaryon irritans in aquaculture.

Copper alloy sheets have been shown to prevent cryptocaryoniasis. Therefore, we studied the potential efficiency of copper alloy mesh (CAM) in aquaculture tanks to prevent cryptocaryoniasis outbreaks. The effectivenesses of CAM against the tomont stage of Cryptocaryon irritans and in protecting fish from cryptocaryoniasis were tested both in vitro and in vivo. The mortality rate of C.irritans tomonts increased as the contact time with CAM rose and peaked at 70 min (100% of mortality). Morphological changes were observed such as the shrinking of the protoplasm of the treated tomonts, resulting in a larger gap between the cytoplasm and the cyst wall. Mitochondrial dysfunction due to shrinkage in the inner portion, outer and inner mitochondrial membrane damage and cytoplasmic vacuolation was revealed by ultrastructural analysis. The use of CAM effectively preventing reinfection was also provided. In comparison with group B (infected fish without CAM), both groups A (uninfected fish as a control group) and C (infected fish treated with CAM) had a 100% survival rate until the end of the trial. CAM has the same anticryptocaryoniasis effect as copper alloy sheets but is more advantageous due to its lightweight, reduced labor cost and lower purchase cost. It is noticeable that CAM exposure also prevents the excessive accumulation of copper ions in aquaculture sea water.

Research on Wave and Energy Reduction Performance of Floating Breakwater Based on S-Shaped Runner

Aiming at the breeding environment where the construction of marine pastures requires low wind and waves, a floating breakwater (FB) with a Savonius type (referred to as S type) runner with wave absorption and energy reduction function is studied for wave absorption and energy reduction in aquaculture sea areas. The wave-absorbing and energy-reducing performance of the floating breakwater is studied by the method of combining numerical simulation and experiment. Using Star-CCM+ numerical simulation software, based on linear wave theory and energy conservation law, using overlapping grid technology, calling DFBI model, second-order time discretization, a three-dimensional flow field model of the floating breakwater was established and numerically simulated. At the same time, a floating breakwater physical test system was developed for experimental verification, the transmission wave and the conversion power consumption of the S-shaped runner under different wave heights and different periods were measured, and the results Please carefully check the accuracy of names and affiliations. of numerical simulation and physical experiments were comprehensively evaluated. The research results show that the floating breakwater based on the S-shaped runner has the functions of reducing the wave height and reducing the wave energy, which have guiding significance for practical engineering.

An Embedding Skeleton for Fish Detection and Marine Organisms Recognition

The marine economy has become a new growth point of the national economy, and many countries have started to implement the marine ranch project and made the project a new strategic industry to support vigorously. In fact, with the continuous improvement of people’s living standards, the market demand for precious seafood such as fish, sea cucumbers, and sea urchins increases. Shallow sea aquaculture has extensively promoted the vigorous development of marine fisheries. However, traditional diving monitoring and fishing are not only time consuming but also labor intensive; moreover, the personal injury is significant and the risk factor is high. In recent years, underwater robots’ development has matured and has been applied in other technologies. Marine aquaculture energy and chemical construction is a new opportunity for growth. The detection of marine organisms is an essential part of the intelligent strategy in marine ranch, which requires an underwater robot to detect the marine organism quickly and accurately in the complex ocean environment. This paper proposes a method called YOLOv4-embedding, based on one-stage deep learning arithmetic to detect marine organisms, construct a real-time target detection system for marine organisms, extract the in-depth features, and improve the backbone’s architecture and the neck connection. Compared with other object detection arithmetics, the YOLOv4-embedding object detection arithmetic was better at detection accuracy—with higher detection confidence and higher detection ratio than other one-stage object detection arithmetics, such as EfficientDet-D3. The results show that the suggested method could quickly detect different varieties in marine organisms. Furthermore, compared to the original YOLOv4, the mAP75 of the proposed YOLOv4-embedding improves 2.92% for the marine organism dataset at a real-time speed of 51 FPS on an RTX 3090.

Assessment of Sea-Area Benchmark Pricing: Using Chinese Aquaculture to Evaluate and Revise the Price Structure of Resources

Kong, H.; Shen, J.; Zhao, Y., and Sun, Q., 2022. Assessment of sea-area benchmark pricing: Using Chinese aquaculture to evaluate and revise the price structure of resources. Journal of Coastal Research, 38(5), 925–936. Coconut Creek (Florida), ISSN 0749-0208. China has implemented a system of paid use of sea areas and has in recent years promoted their market-oriented allocation to ameliorate the efficiency and to realize their intensive and economical use. Estimations of the sea-area benchmark price can reveal the differences in sea areas, quality, and efficiency. This study introduces a framework to assess the benchmark price of the sea areas, applied to open aquaculture in Lianjiang County (Fujian Province, China). The assessment results show that the sea area used for bottom-sowing aquaculture in Lianjiang County was classified as Grade 2, whereas the sea area used for raft aquaculture and net cage aquaculture was classified as Grade 4. Upon comprehensive consideration of the theoretical value and the actual demand for sea-area management, the benchmark price of three types of open aquaculture sea areas is evaluated. The benchmark prices for bottom-sowing culture sea areas were found to be RMB 65–117/mu/year; for raft culture sea areas, they were RMB 20–252/mu/year; and for net cage culture, sea areas were RMB 100–800/mu/year. Overall, this study constructed a revised system of sea-area benchmark pricing, considering the natural conditions of the sea area, policy factors, transportation and infrastructure, culture conditions, and development degree. These results could be used as the guiding prices of the government to transfer sea-area resources and could ensure the realization of the economic interests of the government as owner of the sea area. Furthermore, this approach can provide a novel way to evaluate sea-area prices in other coastal areas.

Spatiotemporal Variations in Trace Element Compositions in Pollock Populations under the Influence of Coastal Norwegian Salmon Farms

AbstractPollock Pollachius virens (also known as Saithe) modify their feeding habits when including in their diet uneaten feed pellets from salmon aquaculture sea cages. To determine the influence of salmon farms on Pollock, multivariate and univariate analyses were conducted on the trace element signatures from muscle and liver tissues. Sample fish were caught in the vicinity of salmon farms and in control areas (>3‐km distance from the farms) on the coast of Hitra Island (western Norway) over two consecutive years (2012 and 2013). The hepatosomatic index was calculated as a proxy of fish body condition and was higher in Pollock captured near the salmon farms in both years. Variations in specific trace element profiles revealed the influence of farming on the Pollock assemblages (i.e., arsenic, manganese, and copper in muscle; vanadium and manganese in liver). Differences in element composition between sampling years were notable and may, in addition to influence from salmon feed, reflect temporal variation in Pollock migrations or natural food availability. Multivariate analyses of each sampling year showed significant differences in trace element composition of both tissue types among the Pollock groups. Therefore, trace element assessment is a potential tool for determining the influence of aquaculture on Pollock populations, although other natural sources of variation must be taken into account when considering future aquaculture and fishery management strategies.

The Gut Microbiota of Naturally Occurring and Laboratory Aquaculture Lytechinus variegatus Revealed Differences in the Community Composition, Taxonomic Co-Occurrence, and Predicted Functional Attributes

Sea urchins, in many instances, are collected from the wild, maintained in the laboratory aquaculture environment, and used as model animals for various scientific investigations. It has been increasingly evident that diet-driven dysbiosis of the gut microbiome could affect animal health and physiology, thereby impacting the outcome of the scientific studies. In this study, we compared the gut microbiome between naturally occurring (ENV) and formulated diet-fed laboratory aquaculture (LAB) sea urchin Lytechinus variegatus by amplicon sequencing of the V4 region of the 16S rRNA gene and bioinformatics tools. Overall, the ENV gut digesta had higher taxa richness with an abundance of Propionigenium, Photobacterium, Roseimarinus, and Flavobacteriales. In contrast, the LAB group revealed fewer taxa richness, but noticeable abundances of Arcobacter, Agarivorans, and Shewanella. However, Campylobacteraceae, primarily represented by Arcobacter spp., was commonly associated with the gut tissues of both ENV and LAB groups whereas the gut digesta had taxa from Gammaproteobacteria, particularly Vibrio spp. Similarly, the co-occurrence network displayed taxonomic organizations interconnected by Arcobacter and Vibrio as being the key taxa in gut tissues and gut digesta, respectively. Predicted functional analysis of the gut tissues microbiota of both ENV and LAB groups showed a higher trend in energy-related metabolisms, whereas amino acids, carbohydrate, and lipid metabolisms heightened in the gut digesta. This study provides an outlook of the laboratory-formulated diet-fed aquaculture L. variegatus gut microbiome and predicted metabolic profile as compared to the naturally occurring animals, which should be taken into consideration for consistency, reproducibility, and translatability of scientific studies.

Investigation of the Nutrient and Salinity in a Seaweed Aquaculture Sea Area during Seasonal Operation of Wastewater Treatment Plants

Investigation of the Nutrient and Salinity in a Seaweed Aquaculture Sea Area during Seasonal Operation of Wastewater Treatment Plants

Substrate Types on Habitat Breeding Embryonic Development and Larval Morphometric of Sea Urchin Tripneustes gratilla (Linnaeus 1758)

Hatchery is the main factor that plays an important role in aquaculture sea urchin Tripneustes gratilla (Linnaeus 1758). The quality of sea urchin egg is determined by the absorption of nutrients that carried throughout the gonad development while the quality of nutrients is very likely influenced by the type of food consuming. This research of substrate types on habitat breeding embryonic development and larval morphometric of sea urchin had been done on October - November 2016 at the laboratory of marine, Research Center for Deep Sea, Indonesia Institute of Sciences, Ambon. The Samples taken from three different habitats comprises Hative Besar, Liang and Suli beach. The purpose of this research is to determine the effects of substrate types on habitat breeding embryonic development and larval morphometric of sea urchin. The method that has been used to determine the morphometric was done by measuring the diameter and height of the shell using a digital caliper and total body weight using a digital scale. To observe embryonic development and larval morphometric done by in vitro fertilization through eggs selection then cultured in petri dish at a density of 10ind/ml. The result of this research is the most dominant quantity of embryonic development (72 hours) indicated by culture vessel from Hative Besar meanwhile the least is indicated by Liang. The greatest larval morphometric is indicated by culture vessel from Hative Besar with length and height of larval body further the larval of culture vessel from Hative Besar shown ossification formation.

EFISIENSI PERTUMBUHAN RUMPUT LAUT Caulerpa sp. DENGAN PERBEDAAN JARAK TANAM DI TAMBAK CAGE CULTURE

The objectives of this study are to understand the effect of planting space towards<em>Caulerpa sp</em>seaweedgrowth, and to understand the best planting space towards <em>Caulerpa</em> sp seaweed growth. This research did on October until December 2018 in thefishpond of Brackish and Sea Aquaculture Laboratory PekalonganUniversity. This research used complete randomized design (CRD) which consists of three treatment and three repetition. The treatment that applied are 15 cm, 30 cm, and 45 cm of planting space. The Parameter that observed was an absolute weight growth, and water quality. Based on the result of the research showed that the highest absolute weight growth obtained on the treatment of 30 cm planting space that is 73,23gr, followed bythetreatment of 45 cm planting space that is 58,37 gr, and the last, the treatment of 15 cm planting space that is 52,43 gr. The water quality of maintenance media are, salinity ranges from 25-30 ppt, temperature ranges 29-31<sup>o</sup>C, DO ranges from 3-6, 7 mg/L, PH ranges from (6-8,5), and the brightness is 30 cm. The quality of water during research is good enough to support <em>Caulerpa</em> spseaweed growth.