Bioavailability and Ingestion of Microplastics by Fish Larvae in the Douro Estuary

Microplastic contamination in an urban estuary: Abundance and distribution of microplastics and fish larvae in the Douro estuary

Microplastic ingestion in fish larvae in the western English Channel

Microplastics (MPs) ingestion in wild fish during the early stages remains a field with scarce information and contradictory findings in laboratory studies. This study evaluated whether MPs contamination of larval fish stages begins at the commencement of the exogenous feeding phase and whether different species and ontogenetic development stages exhibit different profiles of MPs contamination. We assessed, for the first time, the presence of MPs in the larval stages of two species: the European sardine (Sardina pilchardus), a marine migrant species, and the common goby (Pomatoschistus microps), an estuarine resident species, inhabiting the Douro Estuary (NW Portugal). In both species, MPs were found even in the yolk-sac stage, when fish larvae still have endogenous feeding and do not actively prey on other organisms. This illustrates that fish larvae are already contaminated at a stage where the mouth is still not fully open, further indicating that MPs were not actively ingested. MPs contamination did not vary between species or throughout the ontogenetic development stages, showing similar levels of contamination and MPs contamination profiles. This novel study provides relevant insights into MPs contamination processes, showing that MPs contamination can occur early in the life cycle of fishes, from hatching onwards. Furthermore, the presence of MPs in fish larvae appears to be more dependent on the MPs that are in higher abundance in the surrounding water than fish larvae preferences or ecological guild, physical characteristics, or even the ontogenetic developmental stage.

Summary1. Studies of mesic temperate and tropical rivers suggest an important role for floodplain habitats as nursery areas for larval and juvenile fishes. In arid‐land rivers the extent and duration of flooding is diminished and habitats and resources used by larval fishes are poorly known. Our study documented habitat and resource use of larval fishes in the Rio Grande, New Mexico, an arid‐land river.2. Spatial and temporal distribution of larval and juvenile fishes and their inferred microhabitat preferences were studied during spring, summer and autumn, 2003. Stable carbon (13C : 12C) and nitrogen (15N : 14N) isotope ratios were measured to identify nutrient sources and characterise trophic positions of young‐of‐year fishes in this system.3. Some fishes recruited during high flows (in spring), whereas others recruited during low‐flow periods in late summer. Regardless of the timing of reproduction, microhabitats with lower current velocity and higher temperature appeared to serve as vital nursery grounds for Rio Grande fishes. Ephemeral backwaters and disconnected side channels held the highest abundance and diversity of larvae and juveniles.4. Stable isotope analyses revealed that fish larvae obtained carbon predominately from algal production in early summer, but used organic carbon derived from emergent macrophytes as river discharge decreased in mid‐summer. This shift may have been facilitated by microinvertebrate prey that grazed down edible algae and then switched to macrophytes in mid‐summer. Nitrogen isotope ratios did not differ among species or early life stages, suggesting that larval and juvenile fishes use similar food resources, especially when restricted to isolated pools in summer.

Migratory fishes of the Mekong Basin are facing challenges from human-induced stressors. Quantifying the patterns of fish’s early life stages provides important information on spawning seasons, spawning and nursery habitats, reproductive strategies, migration and dispersal patterns, and stock status. However, the ecology of the Mekong larval fishes, including patterns and drivers of larval fish dispersal, is not well understood. Here, we investigate the temporal variability of drifting larval and juvenile fish assemblages in the Cambodian Mekong River and identify their environmental drivers using long-term (10 year) daily fish larval/juvenile data collections. We found that, in the Mekong main channel, the larval and juvenile assemblages were dominated by longitudinal migrants from the families Cyprinidae and Pangasiidae. Peak abundance and richness were found to occur in July and August, respectively. We detected a significant decline in larval and juvenile abundance and richness over the study period. Cross-wavelet analysis revealed that water levels always lead larval abundance, but lag richness. In addition, cross-correlation analysis observed that peak abundance and richness occurred eight weeks and one week, respectively, before the peak water level. We also discovered that species abundance and richness had a strongly positive relationship with maximum water levels. Variation in fish larval and juvenile abundance and richness was also related to total phosphorus, nitrate, alkalinity, and conductivity. Maximum water levels and the key water quality parameters (e.g., phosphorus, nitrate, alkalinity, and conductivity) significantly influence larval and juvenile fish abundance and richness patterns. Therefore, safeguarding natural seasonal flows, especially maximum flows associated with the peak flood pulse, as well as maintaining good water quality, are key to the reproductive success of many migratory fishes and effective dispersal of offspring to the lower floodplain for nursing, rearing, and growth. Clean and unregulated rivers support productive and diverse fisheries.

Prey availability plays an important role in determining larval fish survival. Numerous studies have found close relationships between the density of mesozooplankton and larval fishes; however, emerging studies suggest that small-size zooplankton are more important prey for some larval fish species. One arising question is whether the size of zooplankton determines the relationship between zooplankton and larval fish community in natural environments. To address this question, we collected small-size (50–200 μm) zooplankton, mesozooplankton (> 330 μm), and larval fish using three different mesh-size (50, 330, 1000 μm, respectively) nets in the East China Sea, and examined their relationships in density. Both meso- and small-size zooplankton densities showed positive relationships with larval fish density, while the relationship is much stronger for the small-size zooplankton. Specifically, the smallest size classes (50–75 and 75–100 μm) of small-size zooplankton showed the highest positive relationships with larval fish density. Temperature, salinity, and chlorophyll-a concentration did not significantly explain larval fish density. Based on these findings, we demonstrate the importance of considering prey size when investigating prey availability for larval fishes.

Prey availability plays an important role in determining larval fish survival. Numerous studies have found close relationships between the density of mesozooplankton and larval fishes; however, emerging studies suggest that small-size zooplankton are more important prey for some larval fish species. One arising question is whether the size of zooplankton determines the relationship between zooplankton and larval fish community in natural environments. To address this question, we collected small-size (50-200 μm) zooplankton, mesozooplankton (> 330 μm), and larval fish using three different mesh-size (50, 330, 1000 μm, respectively) nets in the East China Sea, and examined their relationships in density. Both meso- and small-size zooplankton densities showed positive relationships with larval fish density, while the relationship is much stronger for the small-size zooplankton. Specifically, the smallest size classes (50-75 and 75-100 μm) of small-size zooplankton showed the highest positive relationships with larval fish density. Temperature, salinity, and chlorophyll-a concentration did not significantly explain larval fish density. Based on these findings, we demonstrate the importance of considering prey size when investigating prey availability for larval fishes.

The importance of soft-bodied zooplankton as predators of fish eggs and larvae was examined during March–June, 1983 in Kulleet Bay, Vancouver Island, British Columbia. The diet of the jellyfish Aequorea victoria was evaluated by gut content analysis of individually collected specimens. Crustacean zooplankters were eaten in lesser proportion, and larvaceans, fish larvae, hydromedusae, and siphonophores were eaten in greater proportion than their presence in the environment. Numerous herring larvae (Clupea harengus pallasi) were consumed, as well as the larvae of fishes in several other families (primarily Pleuronectidae, Cottidae, Scorpaenidae, Stichaeidae, Pholidae, and Gadidae), and the pelagic eggs of flatfish (Family Pleuronectidae). When herring larvae hatched in mid-March, A. victoria medusae in the bay contained an average of 22 herring larvae each, comprising 48% of all ingested prey. The predation rates on herring and other fish larvae were calculated from the numbers of larvae in A. victoria, the digestion times, and the field densities of medusae and larvae. Accordingly, 4 newly-hatched herring larvae∙m−3∙d−1 (0.7%∙d−1) were consumed by A. victoria but few were eaten after April 5–6. Predation on other fish larvae was [Formula: see text] larvae∙m−3∙d−1 during April 5 to May 3, but was not detectable in samples collected during May 9 to June 7. Other soft-bodied predators (ctenophores, chaetognaths, siphonophores, and other hydromedusae) contained few fish larvae.

Methodology optimization to quantify microplastic presence in planktonic copepods, chaetognaths and fish larvae

Surveys were conducted in four seasons in the eastern Beibu Gulf from July 2006 to November 2007, to determine the ichthyoplankton composition, abundance, as well as environmental factors impacted on their spatiotemporal distributions. The fish eggs and larvae were sorted from 303 zooplankton quantitative samples, in which at least 1 order, 60 families, 31 genera and 61 species of fish eggs and larvae were identified. The species number was highest in summer whereas lowest in winter. With the most abundant fish egg (the average density was 2.41 ind./m3), spring was the main spawning season, while the greatest mean density of fish larva was 1.35 ind./m3 in summer. In the whole year around, fish eggs had the trends to aggregate in the nearshore of Guangxi coast, fish larvae were more abundant in the northern water. Relationships between fish eggs and larvae abundance and environmental factors were analyzed by using the Yield-Density model. The spatiotemporal distribution of ichthyoplankton in eastern Beibu Gulf was closely related to the Chl a concentration, and the optimal temperature, salinity and Chl a were 19.4–21.7°C, 31.8–33.1 and 1.5–4.8 mg/m3, respectively. Additionally, the distribution of fish larvae could be effected by ocean currents in summer and autumn.

Microplastics (MPs) are ubiquitous pollutants in marine environments. Among the many detrimental consequences of microplastic pollution, its consumption by marine biota is of particular relevance for human health, due to exposure through the food web. Long-term time-series biotic samples are overlooked sources of information for microplastics research. These collections are extremely valuable for the detection and monitoring of changes in marine environments. However, there are very few long-term studies (>10 years) of the uptake of microplastics by biota. Here, we used Dove Time Series planktonic samples (from 1971 to 2020) to assess the presence and prevalence of microplastics in the English North Sea coast over time. Fish and brachyuran larvae were selected due to their commercial importance and consequent implications for human health. A custom enzymatic digestion method was used to extract microplastics for FTIR-ATR polymer identification. An increasing cumulative trend in MP ingestion was identified. Cellophane and polyethylene terephthalate were the polymer types found most frequently in both taxa. Although a total higher microplastics uptake was observed in fish, consumption was not significantly different between taxa over time. Equally, results were not clearly related to microplastics shape or polymer type. This work did not find significant long-term evidence on the increasing uptake of microplastic particles by zooplankton over time. However, the results of this report identified additives, plasticisers, and other more complex and hazardous compounds that should not be released to the environment (e.g., bis-(2-hydroxyethyl) dimerate, propylene glycol ricinoleate) inside marine biota. The study detailed herein provides a case study for the use of long-term time-series in providing accurate assessments of microplastic pollution in marine biota.

Seasonality of occurrence, foods and food preferences of ichthyoplankton in Biscayne Bay, Florida

Kết quả của bài báo là một phần nội dung của nhiệm vụ độc lập cấp nhà nước “Nghiên cứu cơ sở khoa học nhằm xây dựng các giải pháp phát triển nuôi trồng thủy sản bền vững tại đầm Thị Nại, tỉnh Bình Định” do Viện Hải dương học chủ trì giai đoạn 2008-2010. Kết quả hai chuyến khảo sát vào mùa mưa (11/2008) và mùa khô (4/2009) với 18 trạm thu mẫu ở đầm Thị Nại đã thu được 20.588 trứng và 4.458 cá bột. Mật độ trung bình vào mùa mưa (11/2008) là 3,58 trứng và 49,34 cá bột/100m3; vào mùa khô (4/2009) là 951,38 trứng và 75,54 cá bột/100m3, cao hơn nhiều so với mùa mưa. Có sự khác biệt rõ nét về mật độ trứng cá và cá bột giữa các khu vực nghiên cứu và thời gian khảo sát. Vùng tập trung của trứng cá và cá bột là xung quanh cồn Chim ở giữa đầm và khu vực gần cửa đầm; mùa khô (4/2009) có nhiều loài cá đẻ hơn so với mùa mưa (11/2008). Thành phần trứng cá và cá bột gồm 30 họ thuộc 10 bộ, trong đó trứng cá thuộc họ cá mối (Synodontidae), giống cá cơm trổng (Stolephorus), cá cơm (Encrasicholina) và họ cá trích (Clupeidae) là xác định được, chiếm 13%, riêng họ cá mối chiếm 12,5%. Cá bột có 29 họ, họ cá bống (Gobiidae) chiếm ưu thế 81,58%, tiếp theo là họ cá trích (Clupeidae) chiếm 4,08%, họ cá lon (Blennidae) chiếm 3,68%, giống cá sơn biển (Ambasis sp) chiếm 1,35%. Các họ cá khác mỗi loại chiếm tỉ lệ dưới 1%. Summary: The paper presented as a part of the results belonging to the national independent project “Studying on scientific fundamentals for formulating solutions on sustainable aquaculture development at Thi Nai lagoon, Binh Dinh province” carried out by Institute of Oceanography during 2008-2010. The results of two surveys during the rainy season (11/2008) and dry season (4/2009) with 18 stations within Thi Nai lagoon collected 20588 fish eggs and 4458 fish larvae. The average densities on the rainy season (11/2008) were 3.58 fish eggs and 49.34 fish larvae/100m3; the average densities on the dry season (4/2009) were 951.38 fish eggs and 75.54 fish larvae/100m3, which were much higher than those on the rainy season. There was distinct difference in densities of the fish eggs and larvae according to the surveyed areas and seasons. The high densities of fish eggs and fish larvae were observed at Chim hillock surrounding the center and nearby the mouth of the lagoon; more fish species bred during dry season (4/2009) compared to that during rainy season (11/2008). The composition of fish eggs and larvae included 30 families belonging to 10 orders, in which the fish eggs belonging to Synodontidae, Stolephorus, Encrasicholina and Clupeidae were identified, corresponding to 13%, in which Synodontidae 12.5%. Fish larvae included 29 families, in which Gobiidae 81.58%, followed by Clupeidae 4.08%, Blennidae 3.68%, Ambasis sp 1.35%. Other families, each of them below 1%.

Many species of fish depend on estuaries to complete their development. Most of them have a planktonic early life stage, and adults of the same species often live in a different habitat.The aim was to assess the importance of incorporating data on fish eggs and larvae in systematic conservation planning at the Patos Lagoon estuary, Brazil.Different scenarios, where fish larvae and eggs were or were not included in the systematic conservation planning process, were investigated.An estimate of artisanal fishing revenue was used as an opportunity cost and compared with a spatially homogeneous cost. Cluster analysis was performed to assess the impact of incorporating ichthyoplankton data on the outcomes of estuarine systematic conservation planning.Regardless of the opportunity cost, the spatial plans fell into two clusters – those with and without fish egg and larvae data. This shows that egg and larvae data have a large impact on priorities for conservation actions in space.This approach is the first to combine artisanal fishery economic spatial data with a conservation plan that incorporates early life stages of fishes.In the case of the Patos Lagoon estuary, shallow areas were particularly important for reaching conservation targets in all scenarios. Considering the dynamic nature of these ecosystems, much work needs to be done to devise better methods of spatial planning in estuaries.Copyright © 2015 John Wiley & Sons, Ltd.

SUMMARY 1. Larval fish are gape‐limited predators that forage on prey of specific sizes, and thus may be expected to differentially affect members of a zooplankton community, possibly altering the size‐structure or species composition.2. I used an enclosure experiment to look at the effect of predation by larval bluegill on the dynamics of two zooplankton communities, one dominated by large‐bodied individuals and the other by small‐bodied individuals. Enclosures containing these zooplankton received a zero, low, medium, or high density of larval bluegill predators.3. Increasing larval density had a negative effect on zooplankton abundance and abundance declined similarly in the large‐bodied and small‐bodied communities.4. Zooplankton size‐structure, as estimated by the length of the average zooplankton, increased and then decreased during the experiment, decreasing faster at higher larval fish densities. When zooplankton size‐structure was estimated as the length of the average cladoceran, size‐structure declined in the large‐bodied but not in the small‐bodied community and the greatest decline in size‐structure was seen in the medium and high larval density treatments.5. Ordination of each community using multidimensional scaling (MDS) indicated that the trajectory of change in species composition differed between the presence and absence of larval fish. In both communities, the degree of response by individual taxa depended on the density of bluegill larvae. This effect on zooplankton abundance, size‐structure and community composition suggests that larval fish may make an important contribution to zooplankton dynamics in many lakes and ponds.