China is on the track tackling Enteromorpha spp forming green tide

Green tide management is supposed to be a long term fight rather than an episode during the 29th Olympic Games for China, since it has been gaining in scale and frequency during the past 3 decades in both marine and estuary environment all over the world. A number of rapid-responding studies including oceanographic comprehensive surveys along the coastline have been conducted during the bloom and post-bloom periods in 2008 by Chinese marine scientists. The preliminary results are as below: (1) phylogenetic analysis indicates that the bloom forming alga forms a clade with representatives of the green seaweed Enteromorpha linza, though, the alga has been identified as E. proliera by means of morphological; (2) the present data suggest that the bloom was originated from south of Yellow Sea, but not the severely affected area near Qingdao City; (3) pathways of reproduction for E. prolifera have approved to be multifarious, including sexual, asexual and vegetative propagation; (4) somatic cells may act as a propagule bank, which is supposed to be a very dangerous transmitting way for its marked movability, adaptability and viability; (5) pyrolysis of the alga showed that three stages appeared during the process, which are dehydration (18–20^o^C), main devolatilization (200–450^o^C) and residual decomposition (450–750^o^C), and activation energy of the alga was determined at 237.23 KJ•mol^-1^. Although the scarce knowlegde on E. prolifera not yet allow a fully understanding of the green tide, some of the results suggests possible directions in further green tide research and management

Effect of Mytilus coruscus selective filtration on phytoplankton assemblages

The feeding selectivity of bivalves can play an important role in shaping the structure of phytoplankton communities of natural waters. This could be particularly true in waters with intensive bivalves farming, like Sungo Bay, Northern China. Understanding the role of bivalve feeding behavior is important for assessing how the dense cultivation of bivalves may affect phytoplankton community composition and food web structure in farm areas. In this study, we investigated the feeding selectivity of blue mussel Mytilus coruscus on natural phytoplankton assemblages in Sungo Bay using both optical microscopy and HPLC-pigment analysis. Results showed that cryptophytes dominated the phytoplankton community and made up 66.1% of the total phytoplankton abundance. A comparison of phytoplankton composition between natural and filtered seawater showed that M. coruscus preferred cryptophytes and dinoflagellates than Chaetoceros spp. and Skeletonema spp. Cryptophytes were not detected in gut contents by microscopic observation, while their marker pigment alloxanthin was present, suggesting they were also consumed by M. coruscus and can be readily digested. This highlights the shortcomings of microscopic methods and the significance of HPLC-pigment analysis in obtaining a comprehensive understanding of feeding selectivity of bivalves. The proportions of Chaetoceros spp. and Skeletonema spp. in gut contents were significantly lower than their proportions in the seawater, and contrastingly, the proportions of Cocconeis spp. and Pinnularia spp. showed opposite patterns. The marker pigments prasinoxanthin and zeaxanthin were detected in the gut of M. coruscus indicating that picophytoplankton (e.g., prasinophytes and Synechococcus) are also food sources for this bivalve. This information furthers our understanding of bivalve aquaculture and environment interactions.publishedVersio

The Sediment Selectivity of Perinereis aibuhitensis Larvae: Active or Passive?

The selectivity of Perinereis aibuhitensis larvae on different sediment types was studied using an experimental behavioral device in the lab. There were six types of sediment with different organic matter content: 2.19, 2.30, 2.86, 3.25, 3.51, and 5.52%. The results indicated significant differences in the six treatments’ organic matter content (p < 0.05). When the P. aibuhitensis larvae initially attached to the sediment, the larvae’s density showed no significant difference among the six treatments. The density of larvae decreased gradually during the experimental period. It increased with the increasing organic matter content in sediment at every sampling time, but there was no significant difference (p > 0.05). The larvae’s specific growth rate in the first month was significantly higher than those in the second and third months (p < 0.05). The mortality showed no significance at different sediments in equal sampling times, but the mortality was lower in high organic matter content sediments. This study showed that the P. aibuhitensis larvae did not make an active selection; random selection happened when initially attached to the sediment with different organic matter contents. Higher organic matter content in the sediment was more conducive to larvae survival, and the organic matter content is the limitation factor on the mortality and the density. The different densities in the natural habitat of P. aibuhitensis might occur due to the passive selection by the environment

Bioaccumulation and biochemical patterns of Ruditapes philippinarum clams: responses to seasonality and low contamination levels

Shellfish farming and shellfish harvesting have been practiced for a long time in the Ria de Aveiro coastal lagoon (Portugal). Among commercial bivalves, Manila clam Ruditapes philippinarum represents one of the most important species inhabiting this coastal system. Introduced in Portugal in 1984, naturalised R. philippinarum clam populations have been subjected to several pressures that may threaten this resource sustainable management: illegal fishing, harvesting in chemically polluted sites with impacts on human health and lack of control in terms of productivity with the risk of a progressive decline of the biomass. On behalf of the ASARISAFE project (with the title Safety and sustainable management of valuable clam product in Portugal and China) the environmental quality of Manila clam harvesting sites was evaluated, focusing on inorganic pollution and health status of clams in terms of bioaccumulation as well as biochemical performance. Seasonal sampling campaigns were conducted in six R. philippinarum harvesting areas evaluating inorganic pollution levels, in clam's tissues, sediment and water. Clams biochemical performance in terms of metabolism, energy reserves and oxidative stress was also assessed. The results obtained showed that mercury (Hg) and arsenic (As) were the elements with the highest BAF (Bioaccumulation factor) values, but contamination levels in tissues and sediments varied among sampling areas and seasonal campaigns. The amount of clams consumed per week to exceed Provisional Tolerable Week Intake (PTWI, kg) was the lowest for As, revealing that less 0.05 kg of clams was enough to exceed PTWI. However, the results obtained further demonstrated that the clam's biochemical performance was not responding to tissues contamination levels but were closely related to seasons, with distinct metabolic capacity and oxidative stress levels among distinct sampling periods during the year.publishe

Perspectives on Bivalves Providing Regulating Services in Integrated Multi-Trophic Aquaculture

The concept of integrating species into one culture system originates from Asia and the Middle East. Development of integrated aquaculture involving marine bivalves is relatively new, going back to the late 1980s in China and 1990s in the Western world. In this chapter, we present four cases of integrated multi-trophic aquaculture (IMTA) where bivalves are involved in providing regulating services: i) shrimp culture in ponds, ii) cascading pond systems, iii) open-water caged finfish culture and iv) bay-scale culture systems. The bay-scale integrated culture system in Sanggou Bay in China represents commercial IMTA where a range of different regulating services are provided by the bivalves. Bivalves use degraded fragments derived from cultured kelp and organic waste products from fish farming, and play an important role in the ecosystem processes of the bay. The provision of regulating services in shrimp and cascading ponds is evident as the system configurations allow for biogeochemical processing of waste to maximize extraction by the bivalves. The current configurations used in open-water finfish cage culture suggest that adaptation of concepts allowing for control of effluent water, producing longer contact times and increased biogeochemical processing of the waste products, will dominate future IMTA development. If global bivalve culture production is sustained, we will likely see more regulating services from bivalves in IMTA systems, as new opportunities may arise for developing novel IMTA configurations and concepts

The potential of ocean acidifi cation on suppressing larval development in the Pacifi c oyster Crassostrea gigas and blood cockle Arca infl ata Reeve

We evaluated the effect of pH on larval development in larval Pacific oyster (Crassostrea gigas) and blood cockle ( Arca inflata Reeve). The larvae were reared at pH 8.2 (control), 7.9, 7.6, or 7.3 beginning 30 min or 24 h post fertilization. Exposure to lower pH during early embryonic development inhibited larval shell formation in both species. Compared with the control, larvae took longer to reach the D-veliger stage when reared under pH 7.6 and 7.3. Exposure to lower pH immediately after fertilization resulted in significantly delayed shell formation in the Pacific oyster larvae at pH 7.3 and blood cockle larvae at pH 7.6 and 7.3. However, when exposure was delayed until 24 h post fertilization, shell formation was only inhibited in blood cockle larvae reared at pH 7.3. Thus, the early embryonic stages were more sensitive to acidified conditions. Our results suggest that ocean acidification will have an adverse effect on embryonic development in bivalves. Although the effects appear subtle, they may accumulate and lead to subsequent issues during later larval development

Suitability of two seaweeds, Gracilaria lemaneiformis and Sargassum pallidum, as feed for the abalone Haliotis discus hannai Ino

The suitability of two algae species, Gracilaria lemaneiformis and Sargassum pallidum, for use as food sources for the abalone Haliotis discus hannai Ino was evaluated. Abalones were fed one of five experimental diets: 1) kelp Laminari japonica: 2) G. lemaneiformis: 3) S. pallidum; 4) a mixed diet of L. japonica and G. lemaneiformis (1:1); and 5) a mixed diet of L. japonica and S. pallidum (1:1) for a period of 4 months. The survival, growth (shell length and body weight), condition index (body weight/shell length), and feed utilization were measured. Survival was excellent (100%) in all groups. Growth rate (body weight) was highest in the abalone fed kelp exclusively, followed by the mixed diet of kelp and G. lemaneiformis. The abalone fed S. pallidum had the lowest increase in body weight and the lowest feed intake. The mixed diet of kelp and G. lemaneiformis yielded the biggest increase in shell length. There were no significant differences in the condition index among all the treatment groups. The mean daily feed intake of L japonica was highest, followed by the mixed diets of kelp and G. lemaneiformis, and was lowest for S. pallidum. Abalone exhibited a preference for L japonica. The feed conversion efficiency was highest for G. lemaneiformis. Results suggest that G. lemaneiformis can be used as a partial substitute for kelp in the diet of cultured abalone. (C) 2010 Elsevier B.V. All rights reserved.The suitability of two algae species, Gracilaria lemaneiformis and Sargassum pallidum, for use as food sources for the abalone Haliotis discus hannai Ino was evaluated. Abalones were fed one of five experimental diets: 1) kelp Laminari japonica: 2) G. lemaneiformis: 3) S. pallidum; 4) a mixed diet of L. japonica and G. lemaneiformis (1:1); and 5) a mixed diet of L. japonica and S. pallidum (1:1) for a period of 4 months. The survival, growth (shell length and body weight), condition index (body weight/shell length), and feed utilization were measured. Survival was excellent (100%) in all groups. Growth rate (body weight) was highest in the abalone fed kelp exclusively, followed by the mixed diet of kelp and G. lemaneiformis. The abalone fed S. pallidum had the lowest increase in body weight and the lowest feed intake. The mixed diet of kelp and G. lemaneiformis yielded the biggest increase in shell length. There were no significant differences in the condition index among all the treatment groups. The mean daily feed intake of L japonica was highest, followed by the mixed diets of kelp and G. lemaneiformis, and was lowest for S. pallidum. Abalone exhibited a preference for L japonica. The feed conversion efficiency was highest for G. lemaneiformis. Results suggest that G. lemaneiformis can be used as a partial substitute for kelp in the diet of cultured abalone. (C) 2010 Elsevier B.V. All rights reserved

Feasibility of Integrated Oyster-Sea Cucumber Raft Culture

China is a major aquaculture country, with both the world´s largest aquaculture production and area, especially oyster aquaculture which accounts for 80% of the global production. However, its ascent has had numerous negative implications, requiring the development of more environmentally friendly aquaculture methods. The ecological farming model is gradually being acknowledged and encouraged as it is the result of in-depth investigations of marine ecosystems. "Integrated Multi-trophic Aquaculture" is a well-known environmentally friendly aquaculture model. The application effects have been outstanding, as it boosts high output per unit area, improves the marine environment, and improves material utilization. Filter-feeding shellfish are raised at levels that create considerable biodeposition. Particulate matter is transferred from the upper to the lower layers of the water body. Organic matter accumulates on the seafloor in the form of biological sediments, which badly influences the substrate environment, including releasing ammonia nitrogen, increasing dissolved oxygen consumption, and altering seabed biodiversity. Previous research suggests sea cucumbers absorb large amounts of organic matter-rich sediments, reducing the nutrient load caused by coastal shellfish and fish aquaculture. Therefore, a novel sustainable farming model based on the principle of multi-trophic integrated farming could be developed by using sedimentary sea cucumbers to feed on the biological sediments produced by filter-feeding shellfish. The purpose of this study was to investigate the possibility of an oyster-sea cucumber raft integrated culture. Sea cucumbers were stocked in oyster breeding cages. A raft-style integrated oyster-sea cucumber culture was attempted to improve the breeding method. This method allows oyster biological sediments to be utilized in situ, reducing oyster breeding density and maintaining economic benefits. This comparative culture experiment of integrated oyster (Crassostrea gigas)-sea cucumber (Apostichopus japonicus) raft culture utilized Sanggou Bay and Guazichang as representative oyster farming locations. We stocked C. gigas in the odd-numbered layers and A. japonicus in the even-numbered layers of the oyster cages in polyculture. Even-numbered layers had three levels of chassis: common aquaculture plate, holeless aquaculture plate, and holeless aquaculture plate with non-knot nets. The aquaculture plate was the first variable in the experiment. The stocking density of A. japonicus in each of the even-numbered layers were separated into three levels, 1, 2, and 4 ind./plate. The second variable in the experiment was stocking density of sea cucumbers. The experiment was simultaneously conducted at both sea locations. Therefore, the experimental design consisted of a three-factor and three-level experiment with a total of 18 treatment groups. During the experiment, we examined to content of: chlorophyll a, particulate organic matter, PO43–-P, NO2–-N, NO3–-N, and NH4+-N in both sea locations. The survival rate, growth performance, and condition of C. gigas and A. japonicus were compared. There was no significant difference in the contents of chlorophyll a or particle organic matter between the two marine areas (P > 0.05). There were significant differences in the four nutrient salt contents between the two locations (P 0.05). Only the low-stocking density sea cucumbers grew, with individual weights over 25% higher than that of the high-density individuals. Individual sea cucumber weights and survival rates in the low density treatment groups were considerably higher than those in the high density treatment groups (P < 0.05). The performance of the holeless aquaculture plate considerably exceeded the common treatment group (P < 0.05). The holeless aquaculture plates with sea cucumbers at a density of 1 ind./plate achieved the highest results in this study. The chlorophyll in the sea area of Sanggou Bay remained mostly unchanged in this experiment. However, the chlorophyll in the water region of Guazichang reduced when compared with that of previous data. With the recent rapid growth in the oyster industry in Rushan City, the oyster output may have reached or possibly exceeds the area´s aquaculture capacity. We advise the oyster breeding density in the Rushan sea area to be reduced to lower the breeding risk for farmers while also promoting the breeding industry´s long-term viability. In this experiment, there was no significant difference in oyster growth across the treatment groups, indicating that the integrated oyster-sea cucumber raft culture mode can lower oyster density and reduce environmental impacts. Simultaneously, breeding high-value sea cucumbers compensates for the loss of breeding income induced by the lower oyster breeding density. When compared to bottom-seeded sea cucumbers, this raft cage mode has a higher level of safety and ease of harvest. This method can be used to replenish oyster growing zones with a high density of oysters to boost the aquaculture industry´s health and long-term development

Seawater carbonate chemistry and hatching rate, malformation rate, metamorphosis rate and shell growth of the Pacific abalone in a laboratory experiment

The hatching process of the Pacific abalone Haliotis discus hannai was prolonged at a pH of 7.6 and pH 7.3, and the embryonic developmental success was reduced. The hatching rate at pH 7.3 was significantly (10.8%) lower than that of the control (pH 8.2). The malformation rates at pH 7.9 and pH 8.2 were less than 20% but were 53.8% and 77.3% at pH 7.6 and pH 7.3, respectively. When newly hatched larvae were incubated for 48 h at pH 7.3, only 2.7% of the larvae settled, while more than 70% of the larvae completed settlement in the other three pH treatments. However, most 24 h old larvae could complete metamorphosis in all four pH treatments. Overall, a 0.3-unit reduction in water pH will produce no negative effect on the early development of the Pacific abalone, but further reduction in pH to the values predicted for seawater by the end of this century will have strong detrimental effects

Acute sulphide toxicity in Perinereis aibuhitensis under different salinities and temperatures: LC50 and antioxidant responses

Sulphide accumulates in sediment due to global aquaculture development and is very harmful to aquatic and benthic ecosystems. Perinereis aibuhitensis inhabits coastal areas and is often exposed to fairly high sulphide concentrations. The present study investigated the tolerance of P. aibuhitensis to sulphide to evaluate its potential application in sulphide remediation and sustainable aquaculture. We assessed the toxicity of sulphide on P. aibuhitensis in a 96 h acute sulphide exposure experiment under different temperature and salinity conditions. Two-way ANOVA showed that increasing salinity did not influence the LC50 of P. aibuhitensis exposed to sulphide. In contrast, increasing temperature significantly augmented the LC50 value (p < 0.05). The results showed a negative relationship between mortality and temperature, and between mortality and exposure time. Subsequently, we performed 2-way ANOVA analysis of the antioxidant (superoxide dismutase [SOD], catalase [CAT] and total antioxidant capacity [T-AOC]) responses of P. aibuhitensis during 96 h exposure to sub-lethal sulphide concentrations (0, 80, 160, 320, and 640 µmol l-1), and a subsequent recovery period. The activation of this antioxidant defense system appeared to depend on sulphide concentration and exposure duration and their interaction. SOD, CAT, and T‑AOC showed obvious differences at the beginning and end of exposure. They were steadily restored during the recovery period. The results indicated that P. aibuhitensis adjusts its antioxidant defense system to cope with sulphide contamination. Therefore, these indexes of P. aibuhitensis could be applied to environmental monitoring and bio-restoration at mudflat or intensive aquaculture areas with high sulphide concentrations