臺灣淺海珊瑚礁區大型底泥動物群聚結構研究

Abstract

沉積物中的大型底泥動物（benthic macrofauna）構成海洋食物網的基礎，並在沉積物重整與生物地球化學循環中扮演關鍵角色，也被廣泛認為是環境監測中可靠的生態指標。然而，珊瑚礁沉積物中的大型底泥動物仍鮮少被研究，尤其在臺灣更是資料匱乏。為填補此知識缺口，本研究首次在臺灣的淺水珊瑚礁生態系中進行大空間尺度的系統性量化調查。於2021至2023年間，我們以水肺潛水方式採集體長大於0.5毫米的大型底泥動物，並蒐集23項環境變數，包括8項水文變數、2項人為因子、6項沉積物特性，以及7項代表周圍固著生物（如珊瑚、藻類與海綿）覆蓋率的生態變數。樣區範圍涵蓋北臺灣22站、東台灣10站、墾丁15站、澎湖22站、小琉球9站、綠島12站與蘭嶼8站，共98個樣點。本研究主要聚焦於兩個問題：（1）底泥動物的生物密度、α多樣性（以有效物種數ENS計算）與分類組成在臺灣周圍是否存在空間差異？（2）哪些環境因子最能解釋這些差異模式？ 本研究共採集15,882隻大型底泥無脊椎動物，經鑑定後分為37個高階分類群，橫跨14個動物門。平均生物密度為47,370隻/m²，最高值出現在綠島燈塔，達409,798隻/m²，各站密度普遍高於其他海洋生態系之文獻報導值。平均 ENS為4.7類，最高數值出現在綠島的公館鼻，為9.4類，而區域平均ENS最高則為蘭嶼地區，達到6類。底泥動物的密度、ENS與分類組成在各區域間均呈顯著差異，並呈現明顯的東─西差異，與台灣珊瑚類群組成常見的南─北變化趨勢有所不同。環境因子除了沉積物變數之外，整體上呈現顯著地區差異。其中，水文（例如：波浪能量、有機碳濃度）與沉積物變數（例如：平均粒徑）為對生物密度、ENS及類群組成最重要的解釋因子。我們認為此東─西向的環境與動物群聚梯度可能反映了台灣周遭大範圍海洋性質的差異，特別是來自黑潮系統的作用。 本研究建立了臺灣珊瑚礁沉積物底泥動物群聚的重要生態基線，並突顯其在環境評估中作為補充性指標的潛力。於臺灣珊瑚礁棲地正面臨日益加劇的人為影響及氣候變遷壓力，且保育需求日趨迫切，本研究亦為未來保育與管理提供了重要的科學基礎。

Sediment benthic macrofauna form the foundation of marine food webs, play key roles in sediment reworking and biogeochemical cycling, and are widely recognized as reliable ecological indicators in environmental monitoring. However, benthic macrofauna in coral reef sediments remain poorly studied, particularly in Taiwan. To fill this gap, we conducted the first large-scale quantitative survey of benthic macrofauna in Taiwan’s shallow coral reef sediments. From 2021 to 2023, using SCUBA diving, we sampled macrobenthos (body size > 0.5 mm) in the sediments proximal to coral reefs around Taiwan. We also collected 23 environmental variables, including eight hydrographic, two anthropogenic, six sedimentary, and seven ecological variables representing the coverage of sessile benthos within the reef ecosystems (i.e., coral, algae, and sponge). In total, 98 sites were investigated: 22 in northern Taiwan, 10 in eastern Taiwan, 15 in Kenting, 22 in Penghu, 9 in Xiaoliuqiu, 12 in Lyudao, and 8 in Lanyu. We focused on two main research questions: (1) How do macrofaunal density, alpha diversity (effective number of species, ENS), and taxonomic composition vary across different reef regions around Taiwan? (2) Which environmental factors best explain these variations? In total, 15,882 macrofaunal individuals were collected and identified into 37 higher taxa, spanning 14 Animalia phyla. The average density per site was 47,370 ind./m², which is significantly higher than the macrofaunal density reported in the global dataset for similar water depths. The highest density was recorded at Garden Lighthouse in Lyudao, peaking at 409,798 ind./m². Additionally, the average density in Lyudao was significantly greater than other regions. The average ENS was 4.7 taxa, reaching up to 9.4 taxa at Gongguan in Lyudao. The highest average ENS across regions was found in Lanyu at 6 taxa. The macrofaunal density, ENS, and composition varied significantly across regions, forming a distinct west–east gradient, unlike the common north–south trend observed in coral assemblages. Although the reef sediments were dominated by sandy fractions (> 95%) across the sampling sites, the overall environmental conditions exhibited significant regional variations. Among the selected environmental variables, the hydrographic (e.g., wave energy; particulate organic carbon, POC) and sedimentary (e.g., grain size) variables consistently explained the most variation in density, ENS, and composition. The observed west-east gradient in faunal ordination constrained by environmental variables (e.g., redundancy analysis, RDA) likely reflects dominant, large-scale oceanographic influences, particularly the Kuroshio current system. These findings established a critical ecological baseline for sediment macrofaunal communities in Taiwan’s coral reef ecosystems and underscore their potential as complementary indicators in environmental assessments and management. Given the growing pressures on Taiwan’s reef ecosystems from human activities and global climate change, as well as the urgent need for effective conservation, this study offers a valuable scientific basis for future management and monitoring efforts.