Reise Karsten, Buschbaum Christian, Büttger Heike, Rick Johannes, Wegner K Mathias
Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Wadden Sea Station Sylt, Hafenstr. 43, 25992 List, Bremerhaven, Germany.
BioConsult SH, Schobüller Str. 36, 25813 Husum, Germany.
Mar Biol. 2017;164(4):68. doi: 10.1007/s00227-017-3104-2. Epub 2017 Mar 6.
Invasion trajectories of introduced alien species usually begin with a long establishment phase of low abundance, often followed by exponential expansion and subsequent adjustment phases. We review the first 26 years of feral Pacific oysters around the island of Sylt in the Wadden Sea (North Sea, NE Atlantic), and reveal causal conditions for the invasion phases. Sea-based oyster farming with repeated introductions made establishment of feral oysters almost inevitable. Beds of mussels on mud flats offered firm substrate for attachment and ideal growth conditions around low tide level. mapped on to the spatial pattern of mussel beds. During the 1990s, cold summers often hampered recruitment and abundances remained low but oyster longevity secured persistence. Since the 2000s, summers were often warmer and recruitment more regular. Young oysters attached to adult oysters and abundances of >1000 m were achieved. However, peak abundance was followed by recruitment failure. The population declined and then was also struck by ice winters causing high mortality. Recovery was fast (>2000 m) but then recruitment failed again. We expect adjustment phase will proceed with mean abundance of about 1000 m but density-dependent (e.g., diseases) and density-independent (e.g., weather anomalies) events causing strong fluctuations. With continued global warming, feral at the current invasion fronts in British estuaries and Scandinavian fjords may show similar adjustment trajectories as observed in the northern Wadden Sea, and also other marine introductions may follow the invasion trajectory of Pacific oysters.
外来入侵物种的入侵轨迹通常始于一个低丰度的长期定殖阶段，随后往往是指数增长阶段和后续的调整阶段。我们回顾了瓦登海（北海，东北大西洋）叙尔特岛周边野生太平洋牡蛎的最初26年，并揭示了各入侵阶段的因果条件。海上牡蛎养殖伴随着反复引种使得野生牡蛎的定殖几乎不可避免。泥滩上的贻贝床为牡蛎附着提供了坚实基质，并且在低潮位附近提供了理想的生长条件。其分布与贻贝床的空间格局相匹配。在20世纪90年代，凉爽的夏季常常阻碍幼体补充，丰度一直较低，但牡蛎的长寿确保了种群的持续存在。自21世纪以来，夏季往往更温暖，幼体补充也更规律。幼龄牡蛎附着在成年牡蛎上，丰度达到了每平方米超过1000个。然而，丰度峰值之后是幼体补充失败。种群数量下降，随后又遭遇了导致高死亡率的冰期冬季。恢复很快（每平方米超过2000个），但随后幼体补充再次失败。我们预计调整阶段将以平均每平方米约1000个的丰度进行，但密度依赖（如疾病）和密度独立（如天气异常）事件会导致强烈波动。随着全球持续变暖，英国河口和斯堪的纳维亚峡湾当前入侵前沿的野生牡蛎可能会呈现出与北瓦登海观察到的类似的调整轨迹，而且其他海洋引种可能也会遵循太平洋牡蛎的入侵轨迹。
