臺灣周邊海域微塑膠與仔稚魚季節性的空間分布

Abstract

塑膠製品已成為現今人類社會的必需品，當塑料被棄置且未能妥善處理時，將有很大的機率會隨著水循環進入海洋，再經過物理與化學作用分解而形成直徑介於5毫米至1微米的微塑膠，並受海流推送漂流至各個海域。此外，已有許多研究顯示海洋生物有攝入微塑膠的風險，其中由於仔稚魚為漂浮性魚類(Ichthyoplankton)，各鰭部尚未完善發展故依賴海流的被動輸送，因此當仔稚魚與微塑膠皆受海流推送至同處時，將增加其攝入的風險而造成危害。儘管微塑膠成為新興的環境議題，但我們仍對其在臺灣周圍海域分布特性所知甚少。本研究目的為探討微塑膠在臺灣周邊海域四個水層(表層、葉綠素極大層、中間層與底層)中微塑膠定量與定性的分布情形，與比較季節、離岸距離對微塑膠分布的影響，並進一步了解微塑膠與仔稚魚的空間重疊相關性。本研究於臺灣周邊海域共計39個樣站進行微塑膠及仔稚魚採集，在2021年的春季(四月)與夏季(八、九月)分別收集100份與54份不同樣站及水層的微塑膠樣本。結果顯示，臺灣周邊海域水體中有微型物(包含塑膠材質及纖維素等)的分布，每個樣站中至少有一個水層被觀察到有塑膠材質的微型物。春季時四個水層中的微型物的密度都高於夏季，並且總水體的微型物密度在季節間具顯著差異。雖然在不同水層間的微型物密度無顯著差異，但在近岸處有集中在葉綠素極大層的現象。而以總水體而言，離岸遠近微型物的密度也無顯著差異，但仍能發現遠岸平均密度略多於近岸。此外，仔稚魚與微型物空間分布並未有顯著相關性，是否受水層計算影響或其分布機制確實不同，仍待後續剖析。本研究希望藉此了解臺灣周邊海域在不同深度下可能受微塑膠污染情形，並同時了解生物與環境污染的相互影響，提供臺灣海域管理與保育的重要參考。

Plastic products have become more necessary in human society. When plastics are discarded and mishandled, they have high possibilities to enter the ocean, and after physical and chemical decompositions, their sizes would range from 5 mm to 1μm, which are then called “microplastics”. Microplastics are transported by ocean currents and arrived at various sea areas. Many studies had shown that marine organisms can ingest microplastics. Larvae are ichthyoplankton, whose fins have not fully developed, and are also passively transported by ocean currents. When microplastics and larvae co-occur, the larvae may increase the risk of ingestion and cause harm. Although microplastics are an emerging environmental issue, little is known about their distribution characteristics in the waters around Taiwan. The objectives of this study included: (1) to investigate microplastics density in the four water layers (surface layer, chlorophyll maximum layer, middle layer, and bottom layer, respectively), (2) to compare differences in microplastic distributions between seasons and distance from shore, and (3) to understand spatial correlations between microplastics and larvae. In this study, I collected a total of 100 microplastic samples from 39 stations in spring (April) and summer (August-September), 2021. The results showed that microparticles (including both plastic materials and cellulose.) were observed in all stations around Taiwan. The microplastics could be found in at least one water layer in each station. The average density of microparticles was significantly higher in spring than in summer in all water layers. A higher density of microparticles at the chlorophyll-a maximum layer in the nearshore was found than other water layers, despite no significant differences among water layers. There were no significant density differences of microparticles when comparing distances to shore, although a slightly higher density of microparticles was observed in the offshore stations than those in the nearshore. Moreover, merely a limited spatial correlation between microparticles and larvae existed that may be affected by calculation methods of the water layers or due to different dispersal mechanisms. This study improves our understandings of microplastic pollution at different depths in the waters around Taiwan and interactions between marine organisms and environmental contaminants, and can further provide critical references for managing and conserving marine environments around Taiwan.