Effects of irradiance of various wavelengths from light-emitting diodes on the growth of the harmful dinoflagellate <Emphasis Type="Italic">Heterocapsa circularisquama</Emphasis> and the diatom <Emphasis Type="Italic">Skeletonema costatum</Emphasis>

ABSTRACT:   We investigated the effects of specific light wavelengths from light-emitting diodes (LEDs) on the growth of the dinoflagellate Heterocapsa circularisquama , which kills bivalves, and the diatom Skeletonema costatum , which is an important food source for bivalves. Growth of H. circularisquama was obviously inhibited at 590 nm and a photon flux density less than 75 μmol quanta/m²/s. However, growth of S. costatum was not suppressed by irradiance from any LEDs tested from near-ultraviolet to near-infrared wavelengths at 75 μmol quanta/m²/s. The growth rate of H. circularisquama in an experimental treatment group with irradiance provided by both cool-white fluorescent lamps (12:12 h L : D cycle) and a 590-nm LED (continuous irradiance) was 0.43/day. In the control group with irradiance provided only by cool-white fluorescent lamps (12:12 h L : D cycle), the growth rate was 0.63/day, indicating that growth of H. circularisquama was suppressed by 590 nm (less than 75 μmol quanta/m²/s) irradiance from the LED and the continuous irradiance. The use of 590-nm LEDs in bivalve culture at irradiance levels less than 75 μmol quanta/m²/s might encourage the growth of the useful diatom S. costatum without stimulating growth of the harmful dinoflagellate H. circularisquama .     

Perception of light intensity by Haliotis discus discus based on locomotor activity patterns

ABSTRACT:   An apparatus to measure the locomotor activity of aquatic benthic organisms at variable low light levels was developed and the diurnal behavioral pattern of the abalone Haliotis discus discus was measured at various low light intensities. During the experiment, abalone were exposed to 12 h light–dark cycles of complete darkness, 0 µmol/m²/s throughout the 12 h dark cycle and, during periods I (days 1–8) and III (days 19–26), the 12 h light cycles were set at 10 µmol/m²/s. During period II (days 10–17), abalone were exposed to a light level during the 12 h light cycles of 1 × 10⁻⁵, 1 × 10⁻⁶, 1 × 10⁻⁷ or 1 × 10⁻⁸ µmol/m²/s and the changes in locomotor activity assessed. At daytime levels of 1 × 10⁻⁵ µmol/m²/s, typical behavioral patterns were observed of high locomotory activity during the night-time cycle. However, at lower light intensities, the distinction between day and night activity patterns became less clear and, at intensities lower than 1 × 10⁻⁷ µmol/m²/s, the difference between activity during the light and dark cycles became negligible. Based on this, we conclude that the threshold of light level perception in relation to locomotor activity is approximately 1 × 10⁻⁷ µmol/m²/s. The significance of these results in relation to the entrainment of behavior in abalone is discussed.     

Growth Characteristics of a Neurotoxin-Producing Chloromonad Fibrocapsa japonica (Raphidophyceae)

The effects of temperature, salinity, irradiance and pH on the growth of Fibrocapsa japonica (Raphidophyceae) were examined to determine how environmental factors affect the distribution of this species. Optimal growth was observed at temperatures of 15–25 C, salinities of 25–35 parts per thousand (ppt), irradiances of 60–140 μmol quanta/m² per s and pH between 7.5–8.5. Growth did not occur at temperatures below 10 C or above 30 C nor at salinities below 15 ppt. Fibrocapsa japonica grew when subjected to irradiances of 20–180 μmol quanta/m² per s, and could tolerate a pH range of 6.5–8.5.     

Bioencapsulation of erythromycin using adult brine shrimp, Artemia franciscana (Latreille)

Live adult brine shrimp, Artemia franciscana (Latreille), were enriched with erythromycin to determine if Artemia could accumulate therapeutic levels for subsequent feeding to young fish. Three trials were conducted to determine the erythromycin incorporation and survival rates of enriched Artemia when fed either liposomes containing erythromycin or various erythromycin suspensions. Erythromycin concentration in Artemia fed a liposome suspension was low (∼ 5 μg mL⁻¹) relative to Artemia fed the direct suspension (> 100 μg mL⁻¹) over the same time period. When enriched with suspensions up to 1 g erythromycin L⁻¹ sea water for 14 h, Artemia survival was not significantly affected ( P > 0.05) relative to controls. Using a suspension of 1 g L⁻¹, tissue erythromycin concentrations of 109 ± 16 μg erythromycin mL⁻¹  Artemia homogenate (mean ± SEM) were achieved after 12 h. Concentrations above 170 μg mL⁻¹ were obtained using suspensions of 2–5 g L⁻¹, but Artemia survival significantly ( P < 0.05) decreased.     

Herpesviral haematopoietic necrosis virus (CyHV-2) infection: case studies from commercial goldfish farms

Herpesviral haematopoietic necrosis is a disease of goldfish, Carassius auratus , caused by Cyprinid herpesvirus-2 (CyHV-2) infection. Quantitative PCR was carried out on tissue homogenates from healthy goldfish fingerlings, broodfish, eggs and fry directly sampled from commercial farms, from moribund fish submitted to our laboratory for disease diagnosis, and on naturally-infected CyHV-2 carriers subjected to experimental stress treatments. Healthy fish from 14 of 18 farms were positive with copy numbers ranging from tens to 10⁷ copies μg⁻¹ DNA extracted from infected fish. Of 118 pools of broodfish tested, 42 were positive. The CyHV-2 was detected in one lot of fry produced from disinfected eggs. Testing of moribund goldfish, in which we could not detect any other pathogens, produced 12 of 30 cases with 10⁶–10⁸ copies of CyHV-2 μg⁻¹ DNA extracted. Subjecting healthy CyHV-2 carriers to cold shock (22–10 °C) but not heat, ammonia or high pH, increased viral copy numbers from mean copy number (±SE) of 7.3 ± 11 to 394 ± 55 μg⁻¹ DNA extracted after 24 h. CyHV-2 is widespread on commercial goldfish farms and outbreaks apparently occur when healthy carriers are subjected to a sharp temperature drop followed by holding at the permissive temperature for the disease.     

Relationships between critical photon irradiance for growth and daily compensation point of juvenile Sargassum macrocarpum

SUMMARY: This study was designed to determine the critical photon irradiance for growth and daily compensation point of juvenile Sargassum macrocarpum . Sampling and measurement of natural light conditions were carried out in the S. macrocarpum population at a depth of 8 m off Kiwado in Fukawa Bay, Yamaguchi Prefecture, Japan, from April to June 1998. Photosynthesis and respiration of the juvenile thalli, and diurnal changes in solar irradiance were measured for the same period. The critical photon irradiance for growth of the juvenile thalli observed on the population floor was 1.0–1.5% on the sea surface. The photosynthetic rate of leaf of juvenile thalli increased linearly with increasing photon irradiance when light levels were lower than 50 μM/m² per s. The respiratory rate and light compensation point of the juvenile thalli were 2.49 μL O₂/cm² per h and 4.98 μM/m² per s, respectively. The daily compensation point was estimated with a mathematical model based on photosynthesis–light equations and diurnal changes in solar irradiance. For a day of average solar irradiance over the period of the present study, the estimated daily compensation point of the juvenile thalli was 1.3% on the sea surface. This value agreed well with the observed critical photon irradiance for growth of juvenile S . macrocarpum on the population floor. The results of the study confirm that the mathematical model is effective for estimating the daily compensation point.     

Nutrient requirement for zoospore formation in two alariaceous plants Undaria pinnatifida (Harvey) Suringar and Alaria crassifolia Kjellman (Phaeophyceae: Laminariales)

ABSTRACT:   Sporophyll formation in two alariaceous plants, Undaria pinnatifida and Alaria crassifolia , was studied in relation to the nutrient requirements. The sporophylls of U. pinnatifida formed zoosporangia when they had N and P contents greater than 1.4 kgN/m³ and 0.74 kgP/m³. This indicates that these values are the critical nutrient levels for zoospore formation in U. pinnatifida . In the sporophytes of A. crassifolia , many sporophylls with zoosporangia showed nutrient contents higher than 6.25 kgN/m³ and 1.70 kgP/m³. These results suggest that the U. pinnatifida can form zoospores at lower levels of N and P contents than A. crassifolia . Both species often formed zoosporangial sori on the blades in the late period of each reproductive season. The fertile parts of the blade showed N and P contents higher than the critical levels. This phenomenon indicates that the blades have the capability to form zoosporangial sori if there is a sufficient accumulation of nutrients for zoospore formation. The zoospore formation on the blade seems to be accomplished by an overflow of excess nutrients from sporophylls into the blade, or by accumulating sufficient nutrients to form sori even if the sporophylls are not formed.     

Quantitative real time PCR for the measurement of white spot syndrome virus in shrimp

Quantitative real time PCR, recently developed in molecular biology, is applied in this paper to quantify the white spot syndrome virus (WSSV) in infected shrimp tissue. The WSSV content in moribund shrimp of all species tested ( Penaeus stylirostris, P. monodon, P. vannamei ) ranged from 2.0 × 10⁴ to 9.0 × 10¹⁰ WSSV copies μg^–1 of total DNA ( n =26). In whole moribund post-larvae, 4.3 × 10⁹ WSSV copies μg^–1 of DNA were detected which is equivalent to 5.7 × 10¹⁰ WSSV copies g^–1 of post-larvae. The comparison of WSSV content between different tissues showed that muscle and hepatopancreas tissues contained 10 times less virus than gills, pleopods and haemolymph. With inocula of known virus content, bioassays by immersion challenge showed that a minimum of five logs of WSSV copies was necessary to establish disease in the challenged shrimp. In contrast, five logs of WSSV copies injected into shrimp muscle produced a LT-50 of 52 h. This real time polymerase chain reaction (PCR) technique is sensitive (four copies), specific (negative with DNA from shrimp baculoviruses and parvoviruses), dynamic (seven logs) and easy to perform (96 tests in <4 h).     

Evaluation of coral bleaching condition <Emphasis Type="Italic">in situ</Emphasis> using an underwater pulse amplitude modulated fluorometer

ABSTRACT:   Photosynthetic activities of hermatypic corals (28 genera, c . 68 species and c. 92 specimen) were measured in November 2000 at Sekisei lagoon, Okinawa, Japan, using an underwater pulse amplitude modulated fluorometer. Maximum quantum yield (Fv/Fm) ranged from 0.61 to 0.70 and had an average value of 0.664 (standard deviation [SD], 0.0289). Following the measurement of Fv/Fm, quantum yield (Fm'-F)/Fm' at eight-leveled actinic-light intensities were obtained from all specimens. Values of electronic transport rates (ETR) were nearly the same under low photosynthetic active radiation (PAR; µmol quanta/m² per s) condition and varied with increasing PAR. The value of ETR at 100 µmol quanta/m² per s ranged from 21.3 to 30.0 and had an average of 27.8 (SD, 2.09). In August 2001, a coral bleaching event was observed in Sekisei Lagoon. During the event, photosynthetic activities of 21 specimens of eight species (seven genera) were measured. By applying two indicators, Fv/Fm and ETR at 100 µmol quanta/m² per s obtained in August 2000, 18 of 21 specimens were suggested under the bleaching process. In case of Porites lutea , seven colonies were visually evaluated for their condition of bleaching and were found to have two 'normal', three 'slightly bleached' and two 'heavily bleached'. From the density of zooxanthellae, colonies evaluated 'normal' or 'slightly bleached' did not show an apparent difference. However, they were clearly identified by Fm/Fv and ETR at 100 µmol quanta/m² per s.     

Survival and movement of hatchery-reared red snapper on artificial habitats in the northern Gulf of Mexico

Abstract  Hatchery-reared age-0 red snapper, Lutjanus campechanus (Poey), were released onto artificial habitats in the Gulf of Mexico. Fish showed 12.7% survival after 7 months on small habitats (0.86 m³) and 3.1% survival after 8 months on large habitats (3.9 m³). Emigration was estimated by the movement of fish to unstocked habitats and accounted for 76.8% of the total decline in abundance at release sites after 26 days. Fish showed higher survival and growth rates on small habitats (27.6% at 26 days; 0.33 mm day⁻¹) compared with large habitats (13.2% at 34 days; 0.26 mm day⁻¹), which may have been due to increased predation and competition on large habitats. Fish became evenly distributed among adjacent habitats 26 days after release, indicating that stocking densities at release habitats were above carrying capacities. These observations suggested that providing additional habitat around red snapper release sites would increase survival.     

Physiological differences between the nutrient uptakes of Kjellmaniella crassifolia and Laminaria japonica (Phaeophyceae)

SUMMARY: The nutrient uptake kinetics of Kjellmaniella crassifolia and Laminaria japonica were determined under a variety of conditions. The nitrate and phosphate uptake rates followed Michaelis–Menten kinetics toward ambient nutrient concentrations, showing no difference between the maximum uptake rates of the two species. However, half-saturations of nitrate and phosphate uptake kinetics in K. crassifolia were higher than those in L. japonica . Low water temperature (5°C) greatly restrained the nitrate and phosphate uptakes of both algae. Low irradiance (< 100 μE/m² per s) restrained nitrate and phosphate uptakes only in L. japonica , although high irradiance (> 100 μE/m² per s) caused no difference between the two species. The nitrate and phosphate uptake rates at low irradiance in K. crassifolia were 2–7 times higher than those in L. japonica . Light compensation and saturation irradiances in K. crassifolia were significantly lower than in L. japonica . These results indicate that K. crassifolia is able to take up carbon and nutrients at low irradiance, which suggests that the nutrient uptake characteristic of K. crassifolia could allow it to adapt to deeper habitats and even to high water turbidity.     

Effects of temperature, salinity and irradiance on the growth of the toxic dinoflagellate Gymnodinium catenatum (Dinophyceae) isolated from Hiroshima Bay, Japan

ABSTRACT: Temperature and salinity ranges in which Gymnodinium catenatum (Hiroshima Bay strain) showed specific growth rates higher than 0.2/day were approximately 20–30°C and 20–32. The specific growth rate (μ), expressed as a polynomial equation as functions of temperature ( T ; °C) and salinity ( S ) were μ = (−6.84 × 10⁻⁴ T ² + 0.0354 T – 0.213) × (−1.03 × 10⁻³ S ² + 0.0579 S – 0.548)/0.31; the maximum growth rate (0.31/day) was obtained at 25°C and 30. From a comparison with field data recording temperature, salinity and light intensity, this species may be expected to bloom from summer to autumn in Hiroshima Bay.     

The efficacy of emamectin benzoate as an oral treatment of sea lice, Lepeophtheirus salmonis (KrÒyer), infestations in Atlantic salmon, Salmo salar L.

The efficacy of emamectin benzoate as an oral treatment of sea lice, Lepeophtheirus salmonis (KrÒyer), infestations in Atlantic salmon, Salmo salar L., was evaluated in a dose titration study and two dose confirmation studies. Replicated groups of salmon with induced infestations of sea lice were given emamectin benzoate on pelleted feed at doses of 0, 25, 50 and 100 μg kg⁻¹ biomass day⁻¹ for seven consecutive days. Sea lice were counted at 7, 14 and 21 days from the start of treatment, and comparisons made with control fish given the same diet without emamectin benzoate. Total numbers of sea lice were significantly reduced at all doses in all three studies when compared to control fish. There was no significant difference between doses of 50 and 100 μg kg⁻¹, but the 50 μg kg⁻¹ dose resulted in significantly fewer lice than the 25 μg kg⁻¹ dose. Emamectin benzoate was highly effective in reducing numbers of preadult and adult lice and prevented the maturation of chalimus to motile stages. The optimum therapeutic dose was selected as 50 μg kg⁻¹ day⁻¹ for seven days. Treatment reduced the incidence of epidermal damage by sea lice and, in one study, survival of treated fish was 48% higher than in control groups. No fish mortalities or adverse effects were attributed to treatment with emamectin benzoate at any of the doses tested.     

Multigenerational effects of 17β-estradiol and nonylphenol on euryhaline cladoceran <Emphasis Type="Italic">Diaphanosoma celebensis</Emphasis>

ABSTRACT:     The effects of parental exposure to 17β-estradiol (E2) and 4-nonylphenol (4-NP) on life history parameters of three successive generations of the euryhaline cladoceran Diaphanosoma celebensis were assessed under laboratory conditions. Less than 24-h-old neonates (P) were exposed to five sublethal concentrations of E2 (0.1, 1, 10, 100 and 1000 μg/L) and 4-NP (0.01, 0.1, 1, 10 and 50 μg/L) at 25°C. Age at first reproduction, reproductive period, fecundity and lifespan were investigated. Successive generations (F₁–F₃) were monitored further in the absence of toxicants. Results showed that cladocerans exposed to 10–1000 μg/L E2 produced more neonates at a younger age compared to the control. The same effects were also observed in the F₁ and F₂ but ceased in F₃. Cladocerans exposed to 1 μg/L 4-NP also produced significantly more neonates compared to the control, but this effect was not found in successive generations. The results suggest that vertebrate hormone can modify the reproduction of D. celebensis , and the effects are multigenerational.     

Hormone injections enhance the tolerance of land-locked ayu spermatozoa to cryopreservation

We evaluated the effects of maturation-stimulating hormones on the post-thaw motility of land-locked form ayu ( Plecoglossus altivelis ) spermatozoa. Male ayu were administered three intraperitoneal injections of either salmon pituitary extract (SPE; 0.2 or 0.6 mg g⁻¹ BW day⁻¹) or of 17, 20β-dihydroxy-4-pregnen-3-one (DHP; 2 or 10 μg g⁻¹ BW day⁻¹), the maturation-inducing steroid (MIS) in ayu. Before cryopreservation, the motility of spermatozoa of the SPE- and DHP-treated groups was significantly higher than that of the control group. Similarly, the comparative post-thaw motility (presented as a percentage of the motility obtained before cryopreservation) was significantly higher in the SPE group than in the control; however, there was no significant difference between the DHP group and the control. The effect of SPE and DHP on pre- and post-cryopreservation motility was not dose dependent. Our results suggest that the hormone(s) present in salmon pituitary are effective in enhancing the tolerance of ayu sperm cells to cryopreservation and that the MIS (DHP) is not involved in this process.     

Creation of artificial upwelling areas for brown trout, Salmo trutta, spawning in still water bodies

Abstract  Brown trout, Salmo trutta L., spawning sites were constructed by creating areas of artificial upwelling water, 252 ± 37 mL m⁻² min⁻¹ (95% CL), through appropriately sized spawning gravel substrate in 3 m² vessels buried in the bottom of a 150-m² pond. Natural spawning occurred in the vessels during autumn 2001–2004, with hatching and alevin swim up the following spring. In areas of upwelling, egg survival was 85–95%, while no live eggs were observed in areas without upwelling. In areas with upwelling, the maximum density of live eggs at the eyed stage was 570–1510 eggs m⁻². In spring 2004 and 2005, the density of alevins was estimated at 322 (±187) m⁻² and 567 (±217) m⁻², respectively, in areas with upwelling water, compared with 35.2 ± 25.4 m⁻² in areas without upwelling water in 2004.     

Feasibility of cultivation of Kappaphycus alvarezii (Doty) Doty at different localities on the Northwest coast of India

Kappaphycus alvarezii was cultivated at three places, viz. Mithapur, Okha and Beyt Dwarka on the Northwest coast of India. The biomass and growth rates were measured at 15-day intervals up to 45 days and varied differently for different growth periods at these places. Thus, at 15, 30 and 45 days, the biomass (fresh wt) varied from 182.0±19.96 to 435.0±23.66 g, from 366.0±118.09 to 1096.0±61.43 g and from 530.5±50.95 to 1537.0±43.54 g, respectively, with respective daily growth rates (%) from 3.95±0.78 to 9.80±0.63, from 3.64±0.01 to 13.98±3.07 and from 3.69±0.23 to 6.07±0.06. The seawater temperature, salinity, nitrate and phosphate ranged from 19.3 to 26.9 °C, from 30.81 to 36.83‰, from 11.60 to 19.75 μmol L⁻¹ and from 2.37 to 5.0 μmol L⁻¹ respectively. The growth rate between the culture months was significantly different at Okha at P <0.01. Further, it was significantly correlated to salinity at Mithapur while at Okha and Beyt Dwarka, the same was significantly correlated to nitrate and seawater temperature. Based on this study, commercial cultivation at these localities is quite feasible.     

Annual net production of the five Sargassaceae species in Yoro,western Wakasa Bay,Sea of Japan

ABSTRACT:   Annual net production of the five Sargassaceae species was investigated in Yoro, western Wakasa Bay, Sea of Japan. The Sargassaceae species were collected at a depth of 2.0–2.5 m and subjected to stratified clipping for 13 months. Annual net production was estimated at 2407 g dry wt/m² for Sargassum patens , 2132 g dry wt/m² for Sargassum macrocarpum , 1458 g dry wt/m² for Sargassum siliquastrum , 1197 g dry wt/m² for Myagropsis myagroides , and 1471 g dry wt/m² for Sargassum piluliferum . The ratio of annual net production to maximum biomass (P/B_max) for these species ranged between 1.3 and 1.7, being higher than in previous studies which used the same method. Winter storms with strong wave exposure and relatively calm condition in Yoro were considered to augment P/B_max. The total losses estimated from the different units of stratified clipping were compared. If larger and less segregated units were applied, the total loss would decrease. It was suggested that a 50 cm stratum would be applicable to the larger species (3 m or longer) and a stratum of 20 cm or less would be applicable to mid-sized or smaller species (less than 3 m).     

Effects of salinity and temperature conditions on the reproductive success of turbot (Scophthalmus maximus) in the Baltic Sea

In the Baltic Sea, a large brackish water area, turbot (Scophthalmus maximus) occurs at the border of its distribution with respect to salinity. Using turbot caught in ICES subdivision (SD) 28 (mid-Baltic), salinity requirements for successful egg development were evaluated by assessment of spermatozoa mobility, fertilisation and egg survival at different salinities. Further, to evaluate potential effects of temperatures, egg survival at different temperatures was assessed. Spermatozoa activity and fertilisation rate decreased with decreasing salinity with a significant drop at <7 psu. The viable hatch was significantly lower at <7 psu compared to at 7–15 psu. Hence, due to decreasing salinity this implies lower egg survival in SD 29 and 30 compared to in SD 24–28, and that salinity conditions in SD 31 are insufficient for egg development. Further, following a long period without major inflows of saline water into the Baltic Sea, salinity has decreased. From 1995 onwards salinities <7 psu prevail in SD 27–28 suggesting decreased reproductive success and potentially weaker year-classes in this area. Egg survival was high at 12–18 °C and considerably lower at 9 and 21 °C. Comparing the results with environmental data suggested that spawning time of turbot is adapted to optimum temperatures for egg development, but that occasions with temperatures involving increased egg mortality may occur, e.g. during upwelling situations.     

Detection of transgenic DNA in tilapias (Oreochromis niloticus, GIFT strain) fed genetically modified soybeans (Roundup Ready)

We used nested-polymerase chain reaction (PCR) to detect Roundup Ready soybean in aquatic feeds and feeding tilapias. A template concentration of 10⁻¹⁰ g μL⁻¹ DNA solution could be detected with a dilute degree of 0.01%. Most (90.6%) of the aquatic feeds containing soybean byproduct included exogenous DNA segments. We also compared genetically modified (GM) soybean with non-GM soybean diets in feeding tilapias ( Oreochromis niloticus , GIFT strain) and examined the residual fragments (254 bp) of GM soybeans. Tilapias receiving GM soybean diets had DNA fragments in different tissues and organs, indicating that exogenous GM genes were absorbed systemically and not completely degraded by the tilapia's alimentary canal.