Effect of water mass mixing on phytoplankton dynamics in the scallop culture areas off Okhotsk Sea: A microcosm experiment
閲覧/開く
日付
2022-09Page views
492ASFA keyword
AGROVOC keyword
Taxonomic term
Geographic names
Metadata
アイテムの詳細レコードを表示するShare
抄録
The nearshore (Soya Warm Water (SWW)) and offshore (Intermediate Cold Water (ICW) and Okhostk Sea Low Salinity Water (OSLSW)) waters in the Okhotsk Sea differ substantially in their physico-chemical characteristics. Thus, the extent to which water mass mixing impacts phytoplankton dynamics in the Japanese scallop Patinopecten yessoensis culture areas needs to be assessed to properly manage scallop stocks. This study examined the phytoplankton dynamics in nearshore (SWW) and offshore (ICW and OSLSW) waters and phytoplankton response to water mass mixing (SWW + ICW, OSLSW + ICW) for 5 days in spring (2007) and summer (2007–2009) microcosm experiments. Increased chlorophyll a concentration in ICW was observed due to higher nutrients available for phytoplankton uptake than in OSLSW and SWW at the start of each microcosm experiment. In comparison to spring microcosm, mixing of SWW + ICW promoted higher chlorophyll a concentration and faster Si(OH)4 utilization than in OSLSW + ICW in summer. In addition, the size structure of chlorophyll a differed from micro-size (>) in SWW + ICW to nano-size (<) chlorophyll a in OSLSW + ICW. Suspended particulate organic matter (SPOM) \(\mathsf{\delta^{13}C}\) ratios were positively correlated with chlorophyll a in both mixed microcosms whereas SPOM \(\mathsf{\delta^{15}N}\) isotopic ratios were inversely related to nitrate concentration in SWW + ICW, except in spring. This suggests that stable isotopes can be used in predicting phytoplankton biomass and nutrient utilization. In comparison to microcosm experiments, nearshore water column structure suggests vertical water mixing in summer to autumn when phytoplankton biomass and micro-size fraction were at maximum. Taken together, the advance of nutrient-rich ICW to nutrient-poor nearshore areas in the Okhotsk Sea resulted in increased chlorophyll a biomass and dominance of micro-size phytoplankton in summer, potentially enhancing nutrient and food supply to bottom-cultured scallops as suggested by both microcosm experiments and field observations.
Suggested Citation
Aya, F., & Kudo, I. (2022). Effect of water mass mixing on phytoplankton dynamics in the scallop culture areas off Okhotsk Sea: A microcosm experiment. Regional Studies in Marine Science , 55, 102568. https://doi.org/10.1016/j.rsma.2022.102568
Type
ArticleISSN
2352-4855Collections
- Journal Articles [1267]
Related items
Showing items related by title, author, creator and subject.
-
Seasonal growth, organ indices and food consumption of the Japanese scallop Patinopecten yessoensis (Jay, 1857) in relation to food availability in Tokoro seabed, Okhotsk Sea, North Japan
Aya, Frolan
; Kudo, Isao (The Plankton Society of Japan (The Japanese Association of Benthology), 2022-05-30)
The coastal waters off Tokoro, Okhotsk Sea have been characterized by a substantial decrease in primary production from spring to summer season which will have repercussions on the maintenance of the Japanese scallop Patinopecten yessoensis (Jay, 1857) culture. This study examined the seasonal changes in scallop growth, condition and organ indices in relation to environmental conditions, and compared the sinking particulate organic carbon (POC) flux as an estimate of food availability to scallop food requirements. Monthly specimens were obtained in July 2005, and from May 2006 to December 2008 off Tokoro, Okhotsk Sea. Growth parameters derived from the modified von Bertalanffy growth function of 885 scallop individuals were the mean asymptotic shell height H∞=126.51 mm, Brody growth coefficient K=0.081 year−1, and t0=6.19 year. Condition (CI) and gonadosomatic indices (GSI) increased in April and May, decreased from June to September, but increased again from October until May. The adductor muscle index (AMI) increased from June to October, but declined from November until May when CI and GSI began to increase. Primary production (PP) and chlorophyll a biomass decreased from spring (25.75–29.74 µg C L−1 h−1 and 1.74–5.37 µg L−1) to autumn (0.90–10.83 µg C L−1 h−1 and 0.29–0.75 µg L−1) concurrent with decreasing CI and GSI, but no deleterious effect on AMI was evident during these periods. The sinking POC flux (25–68 mg C m−2 day−1) was low during summer when gonad activity was also low, but started to increase in autumn when gonad activity started to peak. Although a deficit in food availability (lower sinking POC fluxes than scallop food consumption) was observed during summer, the potential advection of organic matter from offshore to nearshore region may have provided additional source of food to bottom-cultured scallops, contributing in part to the increase in shell growth and somatic tissues. -
Ammonia excretion rates of the sea bass, Lates calcarifer, in fresh and sea water
(Society of Israeli Aquaculture and Marine Biotechnology, 1994)The weight-specific ammonia excretion rate of sea bass (Lates calcarifer) fry in fresh water is higher than that of those in sea water. The allometric equation \(y = 24.426 \times ^{-0.4714}\) best describes the relationship between the ammonia excretion rate (y, in µg total \(NH_{3}-N/g/hour)\) and body weight (x, in g wet weight) for fry in fresh water and \(y = 19.891 \times ^{-0.6712}\) for fry in sea water. The ammonia excretion rate of sea bass fry in fresh or sea water did not significantly increase or decrease during prolonged starvation. The pre-feeding ammonia excretion rate of sea bass subadults in fresh water was similar to those in sea water. The ammonia excretion rate of both groups ranged from 3.86 to 4.13 µg total NH3-N per g per hour. Half an hour after feeding, ammonia excretion rates rose to a significant level over pre-feeding values in both freshwater and seawater-adapted subadults. Both groups also showed the same peaks that were 7.5 times higher than pre-feeding levels 3 hours after feeding. By 10 hours after feeding, the ammonia excretion rate of both groups had returned to pre-feeding levels. -
Effects of UV-treated sea water, chlorinated sea water, and formalin-treated copepods on survival and growth of newborn seahorses, Hippocampus comes
(Society of Israeli Aquaculture and Marine Biotechnology (SIAMB), 2011)Seed production of the seahorse Hippocampus comes was examined using different types of sea water (UV-treated, chlorinated, sand-filtered), and formalin-treated copepod Pseudodiaptomous sp. as a food organism. Growth and survival of newborn seahorses (8.9±0.0 mm stretched height, 0.004 g) were monitored until day 30 after birth. Growth (stretched height and weight) was significantly higher (p<0.05) in UV-treated sea water (41.4±0.5 mm, 0.23±0.00 g) than in chlorinated (33.8±1.4 mm, 0.16±0.00 g) or sand-filtered (32.8±0.1 mm, 0.16±0.00 g) sea water. Survival was significantly higher in UV-treated (65.6±1.1%) and chlorinated (62.2±4.0%) sea water than in sand-filtered sea water (41.1±1.1%). Survival of seahorses fed 30 ppm formalin-treated copepods (95.3±1.8%) was significantly higher (p<0.05) than of seahorses fed untreated copepods (78.7±5.5%) on day 8. On day 15 survival was 78.7±9.68% in seahorses fed formalin-treated copepods and 0% in those fed untreated copepods. By day 30, survival of seahorses fed formalin-treated copepods was 64.7±9.82%. On the day of the final comparison (day 10), there was no difference in size between groups. Thus, the present study demonstrates that survival and growth of newborn seahorses is significantly improved in UV-treated water, and survival is markedly maintained by treating food organisms in formalin.
