Dietary changes in the ark clam (Anadara kagoshimensis) is associated with phytoplankton community patterns in a temperate coastal embayment
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Dietary changes in the ark clam (Anadara kagoshimensis) is associated with phytoplankton community patterns in a temperate coastal embaymentWater 2022, 14(21), 3497. https://doi.org/10.3390/w14213497Kang HY, Kim C, Kim D, Kwon KY, Lee WC, Kang CKThe monthly phytoplankton communities and dietary items of the filter-feeding ark clam (Anadara kagoshimensis) in cultivation were examined in a shallow temperate coastal embayment of Yeoja Bay in Korea, to identify dietary changes in clams associated with phytoplankton community patterns. A self-organizing map (SOM) algorithm was applied to shape the community structures of phytoplankton. Clam δ13C and δ15N values were determined monthly and compared with those of phytoplankton, microphytobenthos, suspended particulate organic matter (SPOM), sedimentary organic matter (sedimentary OM), and Phragmites australis. Our SOM clustered monthly phytoplankton communities, revealing a seasonal shift in the dominance of large-sized diatoms (sporadically together with dinoflagellates), which were detected almost year-round, to small-sized taxa (chlorophytes, prasinophytes, and prymnesiophytes), which were observed in May–June. The δ13C and δ15N measurements revealed that pelagic and benthic diatoms serve as the main contributors to the clam diets. A reduction in their dietary contribution accompanied a considerable increment in the contribution of Phragmites detritus in association with the dominance of small-sized phytoplankton during the late spring. Our results suggest that the dominance of small-sized phytoplankton during the critical spring period of the clam life cycle may decrease the availability of preferred items (i.e., size-related food quality) and lead to dietary changes in the clams in relation to climate forcing in this warming sea.
- 등록일2022-11-07 10:48:07
Seasonal energetic physiology in the ark shell Anadara kagoshimensis in response to rising temperature
- 작성자SIEL
- 조회수111
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Seasonal energetic physiology in the ark shell Anadara kagoshimensis in response to rising temperatureFrontiers in Marine Science (2022) 9:981504. doi: 10.3389/fmars.2022.981504Kang HY, Seong J, Kim C, Lee BG, Lee IT, Kang CKKnowledge of physiological responses of important shellfish species to rising temperatures is crucial in assessing the impacts of climate change on marine aquaculture production. The physiological components of energy balance that support growth performance were measured seasonally at different exposure temperatures in the ark clams (Anadara kagoshimensis) cultured in the shallow muddy bottom sediment in Yeoja Bay, Korea. We tested the effects of winter minimum (3–8°C) and summer maximum (23–28°C) temperature elevations on individual physiological processes (ingestion, respiration, egestion, and excretion) and the combined energetic physiology (scope for growth [SFG] and net growth efficiency [K2] measures). The seasonal cycle of dry flesh tissue weight (DW) was also investigated from January 2016 to November 2018, to compare its variation at contrasting cold vs. warm regimes. The rates of physiological components were related to DW, generating significant allometric equations. The weight exponents of the equations for ingestion rate and respiration rate were low at the winter minimum compared with the remaining season temperatures, indicating a higher thermal sensitivity in larger individuals. The physiological rates that were re-calculated for individual components based on estimates of the slope and intercept of the equations increased with increasing temperature, revealing an incapability of thermal acclimation and a temperature effect at seasonally different endogenous conditions. The thermal sensitivity (Q10) of the ingestion rate and respiration rate was reversed between the winter minimum and the summer maximum temperature elevations, yielding negative SFG and K2 values at 3 and 28°C. Furthermore, the interannual difference in the seasonal cycle of clam DW displayed variations in the period of increment prior to spawning and the postspawning loss/recovery in association with its energy balance status in the winter and summer temperature conditions. Overall, these results indicate that warming is projected to affect physiological performance and the seasonal DW cycle of clams in different manners between winter and summer: physiological benefits and advanced weight gain vs. heat stress and progressive weight loss, respectively. The mechanistic adjustment of the clam energy balance across thermal conditions seems to explain the recent advancement in its seasonal biological cycle, as well as the failure in spat collection and the mass summer mortality observed at this culturing site.
- 등록일2022-09-15 17:22:25
Dominance of autochthonous trophic base in northeast Asian stream food webs pre- and post-monsoon
- 작성자SIEL
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Dominance of autochthonous trophic base in northeast Asian stream food webs pre- and post-monsoonEcological Indicators (2022) 142 , 109268. https://doi.org/10.1016/j.ecolind.2022.109268Kang HY, Shin JK, Park HJ, Lee BG, Kang CKSpatial and temporal variability in the trophic base of food webs is an inevitable ecological attribute in aquatic ecosystems with the role of aquatic and terrestrial sources varying from system to system. Despite high algal biomass, an apparent increase in terrestrial detritus during the East Asian summer monsoon would be expected to alter the dominant food web base from the pre- to post-monsoon period. The δ13C and δ15N values of common aquatic invertebrates and fish were compared with those of their potential sources of organic matter across the upstream channel and lacustrine habitats during the pre- and post-monsoon periods in the Se-oak Stream system of Korea. The purpose was to identify the variability in trophic structure (niche and diversity) at the community level and to quantify the contribution of terrestrial and aquatic carbon sources to the food web base. The δ13C and δ15N values of the major potential organic matter sources differentiated allochthonous leaf litter and riparian vegetation from autochthonous biofilm and seston, but with no significant spatial and temporal changes. The δ13C values of consumers fell within a narrower range than that of organic matter sources, consistent with the instream biofilm and seston values. However, the consumer δ15N values spanned a broad range, increasing from invertebrates to fish. The resultant niche overlaps of consumers in the isotopic niche space between seasons and location., their narrower horizontal niche breadths compared to organic matter sources, and the isotope mixing-model estimates indicated that aquatic production was the primary source of organic matter supporting the aquatic food webs. Overall, the results revealed a consistent dominance of autochthonous trophic bases in both lotic and lentic food webs before and after the summer monsoon. Our findings, which highlight the trophic importance of aquatic algal production facilitated by anthropogenic nutrients in this shallow, low-turbidity, and well-illuminated stream food web, may provide insight into ecosystem processes that counteract potential terrestrial-aquatic links to influence food web dynamics based on natural nutrient sources in deep, highly turbid, or shaded stream counterparts.
- 등록일2022-08-20 11:10:09
Impact of Shifting Subpolar Front on Phytoplankton Dynamics in the Western Margin of East/Japan Sea
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Impact of Shifting Subpolar Front on Phytoplankton Dynamics in the Western Margin of East/Japan SeaFrontiers in Marine Science (2021) 8:790703. doi: 10.3389/fmars.2021.790703Dongyoung Kim, Rubao Ji, Hyun Je Park, Zhixuan Feng, Jaebin Jang, Chung Il Lee, Yun-Ho Kang, Chang-Keun KangA subpolar front (SPF) generated between the East Korea Warm Current (EKWC) and the North Korea Cold Current (NKCC) in the western margin of the East/Japan Sea has shifted northward in recent decades. This study investigated the biomassand composition of the phytoplankton assemblage in relation to hydrological and biogeochemical features in the shallow shelf and slope off the Korean coast from January to June in 2016 and 2017, to determine the mechanistic effects of SPFon spring–summer phytoplankton bloom dynamics. Monthly average depth-integrated chlorophyll a (Chl a) levels and the contribution of phytoplankton classes revealed bimodal diatom blooms in early spring and summer in the frontal zone. Canonical correspondence analysis showed that the distribution of high Chl a was associated with cold, low-salinity NKCC water in March 2016. No Chl a peak was observed in March 2017 when the warm saline EKWC water mass invaded. These results suggest that the NKCC intrusion acts as a forcing mechanism leading to enhanced phytoplankton biomass in the frontal zone. In contrast, positive correlations of Chl a concentration with water density and nutrient concentrations suggest that summer blooms were fed by the subsurface chlorophyll maximum (SCM) driven by shoaling of the pycnocline and nitracline. Varying water-column stratification determined the thickness of the SCM layer, driving year-to-year variability in the magnitude of diatom blooms. These findings further suggest that seasonal/interannual variability in the timing of algal blooms affects regional trophodynamics and hence could be an important factor in explaining ecosystemchanges in this region.
- 등록일2021-12-07 11:29:34
Biochemical Composition of Seston Reflecting the Physiological Status and Community Composition of Phytoplankton in a Temperate Coastal Embayment of Korea
- 작성자SIEL
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Biochemical Composition of Seston Reflecting the Physiological Status and Community Composition of Phytoplankton in a Temperate Coastal Embayment of KoreaWater 2021, 13(22), 3221. https://doi.org/10.3390/w13223221Riaz Bibi, Hee Yoon Kang,Dongyoung Kim, Jaebin Jang, Changseong Kim, Goutam K. Kundu, Chang-Keun KangThe biochemical composition of seston along a salinity gradient were examined in the low-turbidity, temperate, estuarine embayment, Gwangyang Bay in Korea. Seasonal variations in sestonic protein (PRT), carbohydrate (CHO), and lipid (LIP) concentrations were analyzed to assess the effects of physiological status and taxonomic composition of phytoplankton. The concentrations of biochemical compounds displayed a close relationship with chlorophyll a (Chla). PRT:CHO ratios were high (>1.0) in the estuarine channel in warmer months and in whole bay in February, indicating a N-replete condition for phytoplankton growth. High CHO:LIP ratios (>2.5) in the saline deep-bay area during the warmer months (>2.0) emphasized the importance of temperature and photoperiod over nutritional conditions. The low POC:Chla (<200), molar C:N (~7) ratios, and biopolymeric carbon concentrations coupled with high primary productivity indicated a low detrital contribution to the particulate organic matter pool. Diatom dominance throughout the year contributed to consistently high carbohydrate concentrations. Furthermore, generalized additive models highlighted that phytoplankton community (i.e., size) structure may serve as an important descriptor of sestonic biochemical composition. Collectively, our results suggest that physiological and taxonomic features of phytoplankton play prominent roles in determining the biochemical composition of seston, supporting the fact that the ecosystem processes in Gwangyang Bay are largely based on phytoplankton dynamics.
- 등록일2021-11-16 17:29:14
Phytoplankton Fuel Fish Food Webs in a Low-Turbidity Temperate Coastal Embayment: A Stable Isotope Approach
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Phytoplankton Fuel Fish Food Webs in a Low-Turbidity Temperate Coastal Embayment: A Stable Isotope ApproachFront. Mar. Sci. 8:751551. doi: 10.3389/fmars.2021.751551Goutam Kumar Kundu, Changseong Kim, Dongyoung Kim, Riaz Bibi, Heeyong Kim, Chang-Keun KangTrophic contributions of diverse OM sources to estuarine and coastal food webs differ substantially across systems around the world, particularly for nekton (fish, cephalopods, and crustaceans), which utilize basal resources from multiple sources over space and time because of their mobility and feeding behaviors at multiple trophic levels. We investigated the contributions of putative OM sources to fish food webs and assessed the spatiotemporal patterns, structures, and trophic connectivity in fish food webs across four seasons from three closely spaced (10–15 km) sites: an estuarine channel (EC), a deep bay (DB), and an offshore (OS) region in Gwangyang Bay, a high-productivity, low-turbidity estuarine embayment off the Republic of Korea. While nearly all previous studies have focused on few representative species, we examined d13C and d15N values of whole nekton communities along with dominant benthic macro-invertebrates, zooplankton, and their putative primary food sources. The d13C and d15N values coupled with MixSIAR, a Bayesian mixing model, revealed that these communities utilized multiple primary producers, but phytoplankton comprised the primary trophic contributor (46.6–69.1%). Microphytobenthos (15.8–20.4%) and the seagrass Zostera marina (8.6–19.8%) made substantial contributions, but the role of river-borne terrestrial organic matter was negligible. Spatially different species composition and stable isotope values, but higher utilization of coastal phytoplankton by estuarine fish, indicated disparate food webs structures between the EC and DB/OS coastal areas, with considerable trophic connectivity. Greater overlaps in fish and cephalopod isotopic niches than among other consumers and a higher estimated carbon trophic enrichment factor for EC nekton confirmed feeding migration-mediated biological transport of coastal OM sources to the estuary. Further, the seasonally consistent structures and resource utilization patterns indicate that fish food webs are resilient to changes at lower trophic levels. Our results contrast with those for other highly turbid coastal systems depending highly on diversified basal sources, including exported terrestrial and wetland detritus alongside autochthonous phytoplankton. Finally, this study provides a novel perspective on the role of OM sources in such low turbidity and highly productive coastal embayments and enhances ourunderstanding of marine ecosystems.
- 등록일2021-10-29 18:06:59
Trophic structures of artificial reef communities off the southern coast of the Korean peninsula as determined using stable isotope analyses
- 작성자SIEL
- 조회수926
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Food web trophic structure at marine ranch sites off the east coast of KoreaHee Yoon Kang, Young-Jae Lee, Changseong Kim, Dongyoung Kim, Doo-Ho Kim, Jun-Ho Kim, Dong-Lim Choi, Chang-Keun KangFront. Mar. Sci. 8:653281. doi: 10.3389/fmars.2021.653281Understanding the trophic ecology of the giant Pacific octopus Enteroctopus dofleini is challenging in developing marine ranches and in reestablishing its regional stocks against the severe stress of fishing. We adopted carbon and nitrogen stable isotope techniques (termed d13C and d15N, respectively) to identify the trophic niche (i.e., pathways and positions) of this species systematically in the entire food webs of two marine ranches off the east coast of the Korean peninsula. While a slight spatial shift in the isotopic nestedness of faunal communities was observed, the d13C and d15N values of consumers were distinct and separate among functional groups at both ranches. The consumer d13C values spanned a broad range between pelagic and benthic sources of organic matter, and their d15N values recorded a stepwise trophic level enrichment, indicating that suspension feeders and herbivore-deposit feeders served as baselines of pelagic- and benthic-based trophic pathways, respectively. The d13C values of predators, including E. dofleini, were arrayed between the two primary consumer groups. Neither d13C nor d15N values showed any remarkable variations with increasing octopus weight. Dietary mixing-model calculations indicated that E. dofleini is a generalist predator relying on both benthic- and pelagic-affinity prey, similar to some teleost species that consume a diverse spectrum of prey. In contrast, other teleost groups showed prevalent trophic links with either pelagic- or benthic-based pathways. The trophic-level estimations revealed that E. dofleini occupies an intermediate position slightly below the teleosts. A lack of discrete trophic positions between E. dofleini and teleosts seemed to be indicative of the released teleost predation but instead reflects the imposed food competition. Overall, the results demonstrated that despite compositional changes in the taxa constituting individual trophic groups, E. dofleini occupied a very similar trophic niche in both ranching systems. Finally, as extracted from information based on octopus marine ranches launched on natural rocky bottoms, our isotopic evidence provides a greater understanding of the trophic ecology of this octopus species in nearshore natural habitats along the southwestern margin of its distribution range.
- 등록일2021-05-20 14:44:26
Trophic structures of artificial reef communities off the southern coast of the Korean peninsula as determined using stable isotope analyses
- 작성자SIEL
- 조회수262
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Trophic structures of artificial reef communities off the southern coast of the Korean peninsula as determined using stable isotope analysesHee Yoon Kang, Byeong-Gweon Lee, Hyun Je Park, Sung-Gyu Yun, Chang-Keun KangMarine Pollution Bulletin 169 (2021) 112474, https://doi.org/10.1016/j.marpolbul.2021.112474The deployment of artificial reefs (ARs) has become a popular technique for creating new hard-bottom habitats, and for enhancing biodiversity and resource abundance for fisheries. We compared colonizing faunal assemblages and reef-associated food-web structures between ARs and nearby natural reefs (NRs) off the Korean coast using stable isotope techniques. Reef communities showed high compositional disparities in colonizing assemblages. Distinct δ13C and δ15N ranges of functional groups could be used to distinguish pelagic from benthic trophic pathways in the reef food web. The isotopic niches of entire faunal assemblages, as well as individual functional groups, overlapped between NRs and ARs, resulting in equivalency for the isotopic functional indices. Mixing model estimates for carnivorous invertebrates and fish suggested strong trophic links to reef-associated faunal prey at both reef types. Finally, these results highlight a convergence in trophic structure between ARs and NRs in accordance with functional diversity in the colonized faunal assemblages.
- 등록일2021-05-19 14:43:22
Assessment of restoration success in a transplanted seagrass bed based on isotopic niche metrics
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- 조회수200
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Assessment of restoration success in a transplanted seagrass bed based on isotopic niche metricsHyun Je Park, Tae Hee Park, Hee Yoon Kang, Kun-Seop Lee, Young Kyun Kim, Chang-Keun KangEcological Engineering 166 (2021) 106239. https://doi.org/10.1016/j.ecoleng.2021.106239A major highlight of restoration efforts is to improve the ecological structure and function of the natural ecosystem in the restored habitat. Assessment of restoration success is a crucial component of an optimal ecological management strategy. In studies to determine the restoration success of a transplanted seagrass habitat by assessing trophic recovery, we examined carbon and nitrogen stable isotope ratios of organic matter sources and macrobenthic assemblages in a transplanted eelgrass Zostera marina bed. The eelgrass bed was restored about 2 years after transplantation in a southern coastal bay of Korea, and consequently, the food web structure in the bed was compared with that in a natural reference site. Our results revealed no significant differences in isotopic values of both macrobenthic consumers and their putative food sources between the transplanted and natural seagrass beds. These isotopic similarities in florae and faunae in the two beds suggest a uniformity in food web structure formed by the diversity and availability of resources, and thereby suggest similarities in the resource–consumer relationship. Isotopic niche indices and high dietary overlaps of feeding guilds in the transplanted and natural beds further suggest the transplanted habitat provides similar ecological functions and ecosystem services to its natural counterpart. Collectively, our results suggest the eelgrass transplantation led to successful restoration of a common seagrass bed, with recovery of the functional properties of the food web structure. Finally, our findings support the idea that stable isotope measures can provide a better understanding of the functioning of restored ecosystems, and improve post-transplantation monitoring efforts for the future planning and managing of successful habitat restoration.
- 등록일2021-04-06 14:40:41
