Gracilaria Cultivation Research Articles

The accumulation and release characteristics of heavy metals on the cultivation environment in Gracilaria litters during decay process

Gracilaria bioremediates heavy metals (Cd, Cr, Pb, Ni, Cu, Zn, Fe, and Mn) and improves water quality in mariculture zones. However, Gracilaria litter produced during the growth and harvest process has become a critical bottleneck problem that limits the sustainable development of the Gracilaria cultivation industry. Experiments of decaying dried (dead) and frozen fresh (falling and dying) G. lemaneiformis and G. lichenosdies were carried out using the litterbag technique under laboratory-controlled and in situ conditions. The results showed that decay rates (k), decomposed time in 50 % (t50) and in 95 % (t95) varied between dried and frozen fresh Gracilaria and were different between G. lemaneiformis and G. lichenosdies. All Gracilaria samples showed an 80 %–90 % weight loss in 15–45 d. The variation in MAIs (accumulation index of metals) between the dried and frozen fresh Gracilaria litters differed significantly and provided evidence that metals could be imported or exported from litter to the environment. Based on our estimates from the 15–45 d experiment, the decay of Gracilaria can release and adsorb heavy metals. The enrichment of Fe, Pb, and Mn was more significant than the release, but the release of Cr, Zn, Cd, Pb, Cu, and Ni was more significant than the enrichment. Heavy metals in Gracilaria litters were accumulated and released simultaneously during decay. The present study simulated and underscores that Gracilaria cultivation intensely influences heavy metals recycled in marine environments It provides a theoretical basis for seaweed management for the sustainable development of the seaweed industry in the mariculture zone.

Pengaruh Metode Budidaya dan Asal Bibit terhadap Pertumbuhan Gracilaria verrucosa Yang Dibudidayakan Di Tambak Desa Kaliwungu, Kabupaten Brebes

Gracilaria verrucosa is one of the seaweeds with good economic value that can be cultivated in ponds. The demand for Gracilaria is increasing as an ingredient for food, beverage, cosmetic, pharmaceutical manufacturing industries. The factors that determine the success of Gracilaria culture: cultivation methods include the seeds quality and source.This study aims to determine the effect of different Gracilaria seeds sources and its culture methods on its growth, to determine the interaction between methods and seed sources. This study aims to determine the effect of different Gracilaria seeds sources and its culture methods on its growth, to determine the interaction between methods and seed sources The research was conducted in October-November 2020 in Kaliwlingi Village, Brebes District, Brebes Regency, Central Java. The experimental used was factorial design with 2 factors: Factor 1: seed sources (A): A1 = Seed from Semarang; A2 = seed from Brebes; A3 seeds from Demak. Factor 2: cultivation method (B): B1 = longline; B2 = off-bottom; B3: broadcast. So there were 9 treatment combinations: A1B1, A2B1, A3B1; A2B1, A2B2, A2B3; A3B1, A3B2, A3B3, each treatment with 3 replications. The data collected include: growth of gracilaria during 60 days. The Specific Growth Rate (SGR) analyzes using ANOVA. The results showed the origin of seedlings and cultivation methods have a very real effect (P<0.05) on SGR Gracilaria. The highest SGR was at treatment A1B1 (Semarang seeds longline method) = 1.84±0.17%/day, and the lowest was treatment A3B3 (Demak seedlings broadcast method) of 0.25±0.13%/day. The water quality measurement results obtained indicate that the water quality at the research location is in a tolerable range for the growth of seaweed. Keywords: Gracilaria, seed source, longline, broadcast, off-bottom.

Diatom assemblages from sediment traps in response to large seaweed Gracilaria cultivation off Nan'ao island, South China

Most previous studies on seaweed bioremediation largely focus on laboratory control tests or short-time, in-situ field experiments. Here we present a dataset from 4-year-long field monitoring (2014–2018) in a mariculture area of the Baisha Bay off Nan'ao Island, South China, attempting to examine how the large seaweed Gracilaria lemaneiformis cultivation affects a mariculture ecosystem. The temporal variation in seawater physicochemical properties (TN, TP, Reactive silicate, CODMn, and chlorophyll α) and sediment proxies (TN and TP) suggest that the Baisha Bay maintained a better water quality during the Gracilaria cultivation periods (December–May) than other months. Additionally, sedimentary diatom assemblages during the Gracilaria cultivation periods showed an increase in Shannon-Wiener values, but a decrease in the dominant Thalassionema nitzschioides abundance, total diatom abundances and P/(A + B) ratios [Planktonic/(Attached + Benthic)]. These changes consistently suggest that Gracilaria cultivation may have helped improve seawater quality and phytoplankton diversity, thereby maintain a healthy mariculture ecosystem.

The production function and profitability analysis of Gracilaria sp. seaweed polyculture with milkfish (Chanos chanos) and black tiger shrimp (Penaeus monodon)

Abstract. Diatin I, Effendi I, Taufik MA. 2020. The production function and profitability analysis of Gracilaria sp. seaweed polyculture with milkfish (Chanos chanos) and black tiger shrimp (Penaeus monodon). Biodiversitas 21: 4747-4754. Gracilaria seaweed is the main ingredient for making agar as a source of food and industry. Gracilaria culture in ponds with a polyculture system is one of the potential seaweed cultivation in Indonesia. This study was aimed to analyze the productivity, production input optimation, and profitability on the polyculture system of Gracilaria sp. with milkfish (Chanos chanos) and black tiger shrimp (Penaeus monodon). The survey method was used to notify the seaweed farmers from Indramayu, West Java, Indonesia. The study data were obtained from all seaweed polyculture farmers populations in the observational location by census containing two farmers groups, namely Gracilaria sp. with milkfish and black tiger shrimp (GMS symbol) and Gracilaria sp. with milkfish (GM symbol) polyculture system. This study resulted that GMS polyculture system obtained higher productivity than GM polyculture system. The GMS business scale was in the increasing return to scale condition, while GM was in the decreasing return to scale condition. The optimal condition of GMS polyculture system was performed by improving the black tiger shrimp seed input, milkfish seed, and milkfish feed, besides declining the working hours, while GM polyculture system was performed by decreasing the milkfish feed and farmers working hours. When the optimal condition is applied to the GMS polyculture system, then the business profit reaches five times, resulting in an increased profit margin of 112% with R/C becomes 134%. Meanwhile, GM polyculture system only reaches 65% business profit, 65% profit margin, and 25% R/C. The investment payback period from both polyculture systems became shorter. The application of production input efficiency on the GMS polyculture system is more prospective than GM polyculture system.

Potential bioremediation effects of seaweed Gracilaria lemaneiformis on heavy metals in coastal sediment from a typical mariculture zone.

Seaweeds are good bio-monitors of heavy metals pollution in coastal seawater. In the present study, the potential bioremediation effects of cultivated Gracilaria lemaneiformis on heavy metals in Nan'ao coastal sediment from a typical mariculture zone, South China were evaluated. Sediment samples were collected from five different zones (Gracilaria cultivation zone, G; Fish culture zone, F; Shellfish culture zone, S; Transition zone, T; Control zone, C) from December 2014 to July 2015. The concentrations of Cd, Pb, Cu, and Zn in the sediments were significantly different among the various types of mariculture areas. The concentrations varied widely: Cd (0.04-1.02) μg g-1; Cu (1.19-37.70) μg g-1; Pb (8.45-74.45) μg g-1; Zn (36.80-201.24) μg g-1. The lowest heavy metal concentrations in the sediment were occurred at Gracilaria cultivation zone, while higher concentrations occurred at control zones and fish culture zones. The pollution load index, principal components and cluster analysis showed that heavy metal concentrations were the highest at fish culture zone, while the concentrations were the lowest at Gracilaria cultivation zone, and Gracilaria cultivation affects the heavy metals in the sediments. Gracilaria had strong adsorption capacities for heavy metals from seawater, showing the highest heavy metal Bioconcentration Factors in May (higher seaweed biomass period). Consequently, the results suggested that Gracilaria cultivation influences the heavy metal concentrations in sediments from the typical coastal mariculture zone. Gracilaria cultivation has the potential to bioremediate heavy metals in the coastal sediments. Therefore, Gracilaria cultivation can add environmental advantages and ecological values to coastal mariculture zones.

Large-scale cultivation of Gracilaria lemaneiformis in Nan'ao Island of Shantou and its effects on the aquatic environment and phytoplankton

PDF HTML阅读 XML下载 导出引用 引用提醒 汕头南澳龙须菜规模栽培对水质和浮游植物的影响 DOI: 作者: 作者单位: 暨南大学生命科学技术学院, 广东 广州 510632 作者简介: 刘之威(1988-),博士研究生,从事大型海藻与浮游植物研究.E-mail:zwliumost@126.com 通讯作者: 中图分类号: S931 基金项目: 公益性行业（农业）科研专项（201403008）；国家自然科学基金项目（41503072）. Large-scale cultivation of Gracilaria lemaneiformis in Nan'ao Island of Shantou and its effects on the aquatic environment and phytoplankton Author: Affiliation: College of Life Science and Technology, Jinan University, Guangzhou 510632, China Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:为研究大型海藻龙须菜（）规模栽培对水质和浮游植物的影响，于2016年3―6月在南澳深澳湾选择龙须菜栽培区（G）、鱼类养殖区（F）和对照区（C）3个采样区域，每个采样区域3个采样点，进行每月1次的采样调查。对海水温度（WT）、盐度（salinity）、pH、溶氧（DO）、总氮（TN）、总磷（TP）、无机氮（DIN）、无机磷（DIP）、叶绿素a（Chl a）和浮游植物密度进行测试分析。结果表明：（1）在龙须菜栽培期和收获期（3―5月），龙须菜栽培区的pH和DO均显著高于其余区域（>0.05）；（2）在龙须菜栽培期（3―4月），栽培区的TN、TP、DIN和DIP含量均显著低于对照区和鱼类养殖区（<0.05），龙须菜收获后（6月），3个采样区域浮游植物的密度大幅上升；（4）2016年南澳海域共收获龙须菜49729 t，据估算，龙须菜规模栽培从海水中移除了2212 t N、174 t P和13300 t C，至少释放了34700 t O2。研究表明，龙须菜规模栽培能有效去除N、P营养盐，防治海洋富营养化；提高栽培区域的pH和DO，有利于防治海洋酸化和低氧问题；降低浮游植物密度，抑制有害藻华的发生。 Abstract:Seaweeds are the major primary producers, and play a vital role in coastal ecosystems. Since 2000, large-scale cultivation of has rapidly developed along the Chinese coast. Nan'ao island is an important base for cultivation in Guangdong. In order to study the effects of large-scale seaweed cultivation on the aquatic environment and phytoplankton, monthly surveys were carried out in the cultivation area of Shen'ao Bay in Nan'ao island from March to June 2016. In this study, fish culture area (F), Gracilaria culture area (G), and control area (C) without cultivation activities were selected for sampling. There were three sampling points per area, marked as F1, F2, F3, G1, G2, G3, C1, C2, and C3, respectively. Four surveys were undertaken on March 25, April 24, May 23, and June 22, 2016. March and April were the cultivation periods, while May was the harvest period, and in June, no was cultured. Dissolved oxygen (DO), pH, total nitrogen (TN), total phosphorus (TP), inorganic nitrogen (DIN), inorganic phosphorus (DIP), phytoplankton density, and chlorophyll a (Chl a) contents were measured. Moreover, the amount of N, P, and C removed from seawater and the amount of O2 released to seawater by were estimated based on the statistical data from Nan'ao in 2016. The results showed that pH and DO in the culture area were significantly higher than those in other regions (>0.05) between the sampling areas after seaweed harvest (June). The contents of TN, TP, DIN, and DIP in the Gracilaria culture area were lower than those in other areas (<0.05) from March to April. Similarly, phytoplankton densities and Chl a contents were significantly lower in the <0.05). The total produce of in Nan'ao island for 2016 was 49729 t, removing 2212 t of N, 174 t of P, and 13000 t of C from seawater while releasing 34700 t of O2 to seawater. Our results show that large-scale cultivation of could effectively remove N and P, improve pH and DO, and inhibit phytoplankton growth. This has the potential to control seawater eutrophication, mitigate the impacts of ocean acidification and hypoxia, and prevent harmful algal blooms. 参考文献 相似文献 引证文献

Ammonia and CO2 enrichment of a Gracilaria cultivation pond through biofiltration of organic waste

Intensive pond cultivation of Gracilaria may achieve maximal yields by enrichment of seawater with ammonia and CO2. In the present study, we examined the use of organic waste material as a source of ammonia and inorganic carbon. A biofiltration system was constructed, consisting of several fermentation tanks and a fluidized bed reactor for the required bioconversion of organic wastes. Gracilaria conferta was cultured in a 30m2 pond from which seawater was circulated through the biofiltration system for a period of nine months. As compared to the filtered seawater used for water supply, the outlets of the fermentation tanks and the fluidized bed reactor showed significant increases in dissolved inorganic carbon and ammonia concentrations and significant decreases in oxygen concentrations and redox potentials. The most efficient organic waste compound tested had the highest C/N ratio. No significant differences were found between the Gracilaria yields of the control and biofiltration pond systems. These results might contribute a fundamental improvement in the economy of Gracilaria pond cultivation by water recycling through such a biofiltration system. Statement of relevanceThe system might contribute a fundamental improvement in the economy of Gracilaria pond cultivation.

Transcriptome analysis identifies genes involved in adventitious branches formation of Gracilaria lichenoides in vitro.

Tissue culture could solve the problems associated with Gracilaria cultivation, including the consistent supply of high-quality seed stock, strain improvement, and efficient mass culture of high-yielding commercial strains. However, STC lags behind that of higher plants because of the paucity of genomic information. Transcriptome analysis and the identification of potential unigenes involved in the formation and regeneration of callus or direct induction of ABs are essential. Herein, the CK, EWAB and NPA G. lichenoides transcriptomes were analyzed using the Illumina sequencing platform in first time. A total of 17,922,453,300 nucleotide clean bases were generated and assembled into 21,294 unigenes, providing a total gene space of 400,912,038 nucleotides with an average length of 1,883 and N 50 of 5,055 nucleotides and a G + C content of 52.02%. BLAST analysis resulted in the assignment of 13,724 (97.5%), 3,740 (26.6%), 9,934 (70.6%), 10,611 (75.4%), 9,490 (67.4%), and 7,773 (55.2%) unigenes were annotated to the NR, NT, Swiss-Prot, KEGG, COG, and GO databases, respectively, and the total of annotated unigenes was 14,070. A total of 17,099 transcripts were predicted to possess open reading frames, including 3,238 predicted and 13,861 blasted based on protein databases. In addition, 3,287 SSRs were detected in G.lichenoides, providing further support for genetic variation and marker-assisted selection in the future. Our results suggest that auxin polar transport, auxin signal transduction, crosstalk with other endogenous plant hormones and antioxidant systems, play important roles for ABs formation in G. lichenoides explants in vitro. The present findings will facilitate further studies on gene discovery and on the molecular mechanisms underlying the tissue culture of seaweed.

Inhibition of marine coastal bloom-forming phytoplankton by commercially cultivated Gracilaria lemaneiformis (Rhodophyta)

While harmful algal blooms (HABs) have become a threat to fisheries, environmental and public health, and economies worldwide, most of the approaches under investigations for prevention, control, and mitigation (PCM) of HABs are limited by high cost and possible secondary pollution. This study reports our laboratory and field experiments demonstrating effective growth-inhibiting effects of the widely cultivated seaweed Gracilaria lemaneiformis on phytoplankton possibly forming HABs. Laboratory experiments demonstrated significant growth-inhibiting effects of fresh G. lemaneiformis thalli in a dose-response manner on four of six test microalgae commonly observed in the seaweed cultivation area (Scrippsiella trochoidea, Prorocentrum micans, Skeletonema costatum, Dunaliella salina) and on the natural phytoplankton assemblage in seawater. Significant inhibiting effects were also observed from in situ bottle (1.0 L) and mesocosm (50 and 1000 L) experiments on the harmful alga Phaeocystis globosa during its blooms. Based on a large-scale field survey, the phytoplankton abundance in the areas with Gracilaria cultivation was demonstrated to be significantly lower than that in the areas without Gracilaria. Collectively, our results showed that large-scale cultivation of G. lemaneiformis is an effective approach to prevent HABs in coastal waters, as an added value to the economically viable industry of Gracilaria cultivation.

Development of a sustainable land-based Gracilaria cultivation system

Copyright © 2014 The Korean Society of Phycology 217 http://e-algae.kr pISSN: 1226-2617 eISSN: 2093-0860 Development of a sustainable land-based Gracilaria cultivation system Jang K. Kim* and Charles Yarish Department of Marine Sciences, University of Connecticut, 1 University Place, Stamford, CT 06901, USA Department of Ecology and Evolutionary Biology, University of Connecticut, 1 University Place, Stamford, CT 06901, USA

Effects of salinity, light intensity and sediment on growth, pigments, agar production and reproduction in Gracilaria tenuistipitata from Songkhla Lagoon in Thailand

SUMMARYThe effects of salinity, light intensity and sediment on Gracilaria tenuistipitata C.F. Chang &amp; B.M. Xia on growth, pigments, agar production, and net photosynthesis rate were examined in the laboratory under varying conditions of salinity (0, 25 and 33 psu), light intensity (150, 400, 700 and 1000 µmol photons m−2 s−1) and sediment (0, 0.67 and 2.28 mg L−1). These conditions simulated field conditions, to gain some understanding of the best conditions for cultivation of G. tenuistipitata. The highest growth rate was at 25 psu, 700 µmol photons m−2 s−1 with no sediments, that provided a 6.7% increase in weight gain. The highest agar production (24.8 ± 3.0 %DW) was at 25 psu, 150–400 µmol photons m−2 s−1 and no sediment. The highest pigment contents were phycoerythrin (0.8 ± 0.5 mg g−1FW) and phycocyanin (0.34 ± 0.05 mg g−1 FW) produced in low light conditions, at 150 µmol photons m−2 s−1. The highest photosynthesis rate was 161.3 ± 32.7 mg O2 g−1 DW h−1 in 25 psu, 400 µmol photons m−2 s−1 without sediment in the short period of cultivation, (3 days) and 60.3 ± 6.7 mg O2 g−1 DW h−1 in 25 psu, 700 µmol photons m−2 s−1 without sediment in the long period of cultivation (20 days). The results indicated that salinity was the most crucial factor affecting G. tenuistipitata growth and production. This would help to promote the cultivation of Gracilaria cultivation back into the lagoon using these now determined baseline conditions. Extrapolation of the results from the laboratory study to field conditions indicated that it was possible to obtain two crops of Gracilaria a year in the lagoon, with good yields of agar, from mid‐January to the end of April (dry season), and from mid‐July to the end of September (first rainy season) when provided sediment was restricted.

Pengaruh Kombinasi Pupuk Kompos dan NPK Terhadap Pertumbuhan, Jumlah Klorofil A dan Kadar Air Gracilaria verrucosa &lt;Br&gt;&lt;I&gt;[Effect Of Compost and NPK Fertilizer Combinations On Growth, Chlorophyll A and Water Content Of Gracilaria verrucose]&lt;I&gt;

AbstractIn general, Gracilaria culture still using organic and inorganic fertilizer single. Organic or inorganic fertilizer applied is felt have not yet enough to support the growth of Gracilaria. The aim of this experiment was to know the best compost and NPK combinations which could influence on growth, chlorophyll a and water content of G.verrucosa. Treatment applied was compost and NPK combinations with different doses, that is A treatment (0 gr/l : 2 gr/l), B treatment (0,5 gr/l : 1,5 gr/l), C treatment (1 gr/l : 1gr/l), D treatment (1,5 gr/l : 0,5 gr/l), E treatment (2 gr/l : 0 gr/l) and F treatment (without fertilizer), each treatment was replicated 4 times. Main parameter observed was daily growth rate (%/day), relative length growth (%), chlorophyll a (ìg/ml) and water content (%) of G.verrucosa. oSupported parameter observed was pH, temperature ( C) and salinity (‰). Data analysis using Analysis of Variance (ANOVA) and Duncan Multiple Range Test. Result of the experiment indicates that compost and NPK combinations with different doses was significantly influence to growth, chlorophyll a and water content of G. verrucosa. The highest mean of daily weight growth rates was C treatment (1 gr/l : 1gr/l) which was equal to 2,56%/day and the lowest mean was F treatment (without fertilizer) which was equal to 1,12%/day. The highest mean of relative length growth was C treatment (1 gr/l : 1gr/l) which was equal to 2,21% and the lowest mean was F treatment (without fertilizer) which was equal to 0,60%. The highest mean of chlorophyll a by the end of the experiment was C treatment (1 gr/l : 1gr/l) which was equal to 0,001948 ìg/ml and the lowest mean was F treatment (without fertilizer) which was equal to 0,001440 ìg/ml. The lowest mean of water content by the end of the experiment was C treatment (1 gr/l : 1gr/l) which was equal to 28,48 % and the highest mean was F treatment (without fertilizer) which was equal to 30,39%.

Pengaruh Kombinasi Pupuk NPK dan TSP Terhadap Pertumbuhan, Kadar Air dan Klorofil A Gracilaria verrucosa &lt;Br&gt;&lt;I&gt;[The Influenced Of NPK and TSP Fertiliter Combination On The Growth, Water Concentration and Chlorophyll A Of Gracilaria verrucosa]&lt;I&gt;

Abstract Gracilaria verrucosa is one of the most potential seaweed and consist of a high economy value. G. verrucosa had been succed cultivated in pond and it produces gel (Lewmanomont, 1995). Gracilaria cultivation in pond generally needs a wide area, easily infected by moss and shellfish so that obstructs Gracilaria’s growth, even decreases it’s quality (Aslan, 1998). One of the solution to solve the problem above is cultivate another seaweed G. verrucosa indoor using the combination of NPK and TSP. NPK and TSP are used to increase growth and formation of chlorophyll a which used to fotosintesis process (Anggadiredja dkk., 2006). The absortion of hara element will add nutrient and influenced to the G. verrucosa’s quality and quantity. This research uses water concentration measuring because gel content measuring is relatively expensive. The goal of this research is knowing the influence of NPK and TSP to G. verrucosa’s growth, water concentration and quantity of chlorophyll a. The result of G. verrocosa shows that daily growth heavy of G. verrocosa in D treatment extremely different (p&lt;0,05) with A, B, C, E and F treatments. The best daily growth heavy of G. verrocosa is in D treatment and the lowest daily growth heavy of G. verrocosa is in A treatment. The result growth length shows that in D treatment extremely different (p&lt;0,05) with A, B, C, E and F treatment. The best growth length is in D treatment and the lowest growth length is in A treatment. The result G. verrucosa’s water concentration shows that in C, D and E treatment extremely different (p&lt;0,05) with A, B and F treatment. The best water concentration is in C, D and E treatment. The lowest water concentration is in A, B and F treatment. The result chlorophyll a quantity shows that in B, C, D E and F treatment extremely different (p&lt;0,05) with A treatment. The best G. verrucosa’s chlorophyll a quantity is in B, C, D, E and F treatment. The lowest G. verrucosa’s chlorophyll a quantity is in A treatment. The conclusion of this research is the combination of NPK and TSP in G. verrucosa seaweed cultivation extremely affect the growth, water concentration and chlorophyll a G. verrucosa with the best dose is 2 g/l and the ratio NPK and TSP is 50%:50%.

Some Aspects of the Growth of Gracilaria birdiae (Gracilariales, Rhodophyta) in an Estuary in Northeast Brazil

The agarophyte Gracilaria birdiae Plastino & Oliveira was cultivated under field conditions in an estuary over a 6-month period. Biomass production varied significantly (p<0.01) and ranged from 900.0 to 3537.0 g m−2 with a mean of 2124.4±1004.36 g m−2 over the cultivation period. The epiphyte-biomass varied from 64.7 to 313 g m−2, with maximum values observed in July. Relative growth rate (RGR) of G. birdiae varying from −0.59 to 4.67% day−1, with a maximum mean observed in July. Correlation analysis showed that RGR was positively correlated with epiphyte-biomass (R-Pearson=0.69; p< 0.01) and negatively correlated with salinity (R-Pearson=−0.41; p<0.05). These correlations were used in a mathematical regression model to estimate the growth of Gracilaria in an estuary. The regression model explained 61% of RGR variability demonstrating that growth rates of Gracilaria were directly related to the variables salinity and epiphytes. The model was developed to help to predict production at a cultivation site in order to evaluate its suitability for Gracilaria cultivation.

Comparison of Spore Inoculated and Vegetative Propagated Cultivation Methods of Gracilaria chilensis in an Integrated Seaweed and Fish Cage Culture

In Chile the integration of Gracilaria chilensis with salmon culture has shown high potential. Seaweed integrated aquaculture is of great interest as it allows waste recycling within fed cage aquaculture. The development of economically feasible suspended methods of seaweed cultivation is therefore of high importance. Hence, production and performance of two suspended Gracilaria cultivation methods, spore inoculated ropes and ropes with twined field collected seaweed, were studied in open water. The production from spore-seeded ropes was comparable to that of twined ropes for the first month of culture. Thereafter, the twined ropes had a significantly higher productivity. Fish farm wastes had no significant fertilizing effect upon Gracilaria growth rate. In addition, spore-originated thalli and field collected thalli were compared under laboratory conditions and in suspended culture using the same cultivation method. Spore-originated thalli had a 50% lower growth rate than the field collected thalli under laboratory conditions; however, no significant differences were detected in the field. Also, the occurrence of spore coalescence growth enhancement was not significant on the spore-seeded ropes. It was concluded that spore-originated cultivation techniques could be of interest for an integrated open seawater aquaculture system due to the high levels of Gracilaria polymorphism. This would result in greater adaptability to environmental variations, and a continuous supply of restocking material.

Correlation between Gracilaria parvispora (Rhodophyta) biomass production and water quality factors on a tropical reef in Hawaii

The factors controlling the growth of the edible, red seaweed, Gracilaria parv ispora Abbott (long ogo), on the south reef of Molokai, HI, were investigated to determine where productive new plantings could be located. Experiments were conducted in October, 1997, and March and June, 1998, in which G. parvispora biomass production was correlated with water quality factors measured at six sites over each 21-day experiment. Water motion, temperature, salinity, nitrate and phosphate varied among sites and experiments, but were not significantly ( P > 0.05) correlated with growth. A strong correlation, however, was found between biomass production and ammonia concentration ( r = 0.91, P < 0.001). Ammonia levels ranged from 0.2–4.0 mmol m –3 over sites and experiments but were skewed towards low values, as was biomass production. The transient nature of ammonia distribution on this reef explains the patchy distribution of locations at which G. parvispora is productive, noticed in previous experiments. Large-scale Gracilaria culture on such a reef would require adding an external source of fertilizer, which may disrupt the reef ecology. An alternative is to develop a dispersed form of cultivation at sites that receive ammonia enrichment from the land, in which case the crop can help absorb excess nutrients entering the reef.

Ecological engineering in aquaculture : use of seaweeds for removing nutrients from intensive mariculture

Rapid scale growth of intensive mariculture systems can often lead to adverse impacts on the environment. Intensive fish and shrimp farming, being defined as throughput-based systems, have a continuous or pulse release of nutrients that adds to coastal eutrophication. As an alternative treatment solution, seaweeds can be used to clean the dissolved part of this effluent. Two examples of successfully using seaweeds as biofilters in intensive mariculture systems are discussed in this paper. The first example shows that Gracilaria co-cultivated with salmon in a tank system reached production rates as high as 48.9 kg m−2 a−1, and could remove 50% of the dissolved ammonium released by the fish in winter, increasing to 90–95% in spring. In the second example, Gracilaria cultivated on ropes near a 22-t fish cage farm, had up to 40% higher growth rate (specific growth rate of 7% d−1) compared to controls. Extrapolation of the results showed that a 1 ha Gracilaria culture gave an annual harvest of 34 t (d. wt), and assimilated 6.5% of the released dissolved nitrogen. This production and assimilation was more than twice that of a Gracilaria monoculture. By integrating seaweeds with fish farming the nutrient assimilating capacity of an area increases. With increased carrying capacity it will be possible to increase salmon cage densities before risking negative environmental effects like eutrophication and toxic algal blooms sometimes associated with the release of dissolved nutrients. The potential for using mangroves and/or seaweeds as filters for wastes from intensive shrimp pond farming is also discussed. It is concluded that such techniques, based on ecological engineering, seems promising for mitigating environmental impacts from intensive mariculture; however, continued research on this type of solution is required.

Ceramialean epiphytism in an intertidal Gracilaria chilensis (Rhodophyta) bed in southern Chile

The cultivation of the agarophytic red alga Gracilaria has become an activity of major importance in several parts of the world. However, Gracilaria cultivation in Chile still faces problems such as epiphytism. We report ceramialean epiphytism abundance, recruitment patterns and the microscopic stages fixed on the Gracilaria thalli in an intertidal bed (Metri bay) of southern Chile. Using a factorial field experiment, we analyze the effect of intertidal elevation and the use of epiphyte free inoculum on the abundance of ceramialean epiphytic algae. This evidence is used to provide management and control recommendations for ceramialean epiphytes.

Fish as potential biocontrollers of Gracilaria (Rhodophyta) culture

Food preferences were studied in 11 fish species in order to find out their potential as epiphyte and copepod controllers in Gracilaria cultures. The fish were exposed to mixtures of Gracilaria and Ulva with other epiphytes included, in the presence of copepods, and the intestinal content of the fish was determined. Aphanius dispar and Tilapia zillii (acclimated to seawater) emerged as potentially useful epiphyte controllers, and Aphanius dispar and Diplodus annularis were potential copepod controllers in Gracilaria cultures.

Epiphytism and fouling in Gracilaria cultivation: an overview

Epiphytism is a major, world-wide problem in Gracilaria cultivation, severely reducing the productivity and cost efficiency of a diverse range of open-water and on-shore farms; the problem is especially acute in tank cultivation systems. The present paper provides an overview of the literature on epiphytism and fouling in the Gracilaria mariculture industry. Topics considered include the identity of the main epiphytes and fouling organisms, aspects of their ecology and biology which contribute towards their success as contaminants, the detrimental effects which epiphytes exert on the host plants, and the range of physical, chemical and biological control methods currently available. Recent changes in approach, with less descriptive information and more emphasis on experimental studies of Gracilaria-epiphyte interactions, are welcomed, as these offer hope for the development of improved control measures.