Centre of Marine Science and Innovation, Ecology and Evolution Research Centre, School of Biological, Earth and Environmental Sciences, University of New South Wales, Sydney, NSW, Australia.
Fisheries Research, NSW Department of Primary Industries, Coffs Harbour, NSW, Australia.
Glob Chang Biol. 2021 Jun;27(11):2537-2548. doi: 10.1111/gcb.15592. Epub 2021 Mar 30.
Climate-mediated species redistributions are causing novel interactions and leading to profound regime shifts globally. For species that expand their distribution in response to warming, survival depends not only on their physiological capacity, but also on the ability to coexist or be competitive within the established community. In temperate marine reefs from around the world, the range expansion of tropical species, known as 'tropicalization', has been linked to the disappearance of temperate habitat-forming kelps and shifts to dominance by low-biomass turfing algae. The consequences of these range expansions and habitat changes on resident fish communities are, however, unclear. Here, we use data derived from baited remote underwater video (BRUV) surveys to analyse changes in diversity and abundance of marine fishes over a 17-year period in warming reefs that have experienced kelp loss (occurring c. 2009). Despite the loss of kelp, we found that species richness and overall abundance of fishes (measured as probability of occurrence and relative abundance), including both tropical and temperate species, increased through time. We also found dramatic shifts in the trophic composition of fish assemblages. Tropical herbivorous fish increased most markedly through time, and temperate-associated planktivores were the only group that declined, a potential consequence of tropicalization not previously identified. At the species level, we identified 22 tropical and temperate species from four trophic guilds that significantly increased in occurrence, while only three species (all temperate associated) declined. Morphological trait space models suggest increases in fish diversity and overall occurrence are unlikely to be driven by uniqueness of traits among tropical range expanders. Our results show more winners than losers and suggest that pathways of energy flow will change in tropicalized systems, as planktonic inputs become less important and a higher proportion of algal productivity gets consumed locally by increasingly abundant herbivores.
气候介导的物种重新分布正在全球范围内引发新的相互作用，并导致深刻的生态系统状态转变。对于那些因变暖而扩大分布范围的物种来说，它们的生存不仅取决于其生理能力，还取决于在已建立的群落中共存或具有竞争力的能力。在世界各地的温带海洋珊瑚礁中，热带物种的范围扩张，被称为“热带化”，与温带生境形成的巨藻消失以及低生物量草皮藻类占优势有关。然而，这些范围扩张和栖息地变化对居住鱼类群落的影响尚不清楚。在这里，我们使用诱饵远程水下视频 (BRUV) 调查的数据来分析在经历巨藻损失（约 2009 年发生）的变暖珊瑚礁中，17 年来海洋鱼类多样性和丰度的变化。尽管巨藻消失了，但我们发现鱼类的物种丰富度和总体丰度（以出现概率和相对丰度衡量），包括热带和温带物种，随着时间的推移而增加。我们还发现鱼类群落的营养组成发生了巨大变化。热带草食性鱼类随着时间的推移增长最为显著，而温带相关的浮游动物是唯一减少的群体，这是以前未确定的热带化的潜在后果。在物种水平上，我们从四个营养群中确定了 22 种热带和温带物种的出现频率显著增加，而只有 3 种（均为温带相关）的物种减少。形态特征空间模型表明，鱼类多样性和总体出现的增加不太可能是由热带扩张者的特征独特性驱动的。我们的研究结果表明，赢家比输家多，这表明在热带化系统中，能量流动途径将会发生变化，因为浮游生物的输入变得不那么重要，而越来越多的藻类生产力会在当地被越来越多的食草动物消耗。
