Data for: Kelp forest loss and emergence of turf algae reshapes energy flow to predators in a rapidly warming ecosystem

Climate change is decimating habitat-forming species in ecosystems around the world. Yet the impacts of habitat loss on the energetics of the wider food web remain uncertain for many iconic ecosystems, including cold-water kelp forests. Here, we assessed how the loss of kelp forests and subsequent proliferation of low-lying turf algae in the Gulf of Maine has altered the trophic niches of, and energy acquired by, predatory reef fishes. Bulk tissue δ13C and δ15N analysis of fish muscle showed that fishes in kelp forests had larger trophic niches and greater interspecific niche separation than did fishes on turf reefs. Moreover, δ13C analysis of essential amino acids revealed that kelp-derived energy accounted for the majority of energy used by forest fishes (>50 % on average), whereas fishes on turf reefs compensated for kelp decline via greater reliance on a phytoplankton-based energy channel. Therefore, ecosystem state shifts to turf algae – now a global phenomenon – may have far-re..., Section 1: Underwater surveys Data1_macroalgae_biomass.csv Data2_roving_fishes.csv Macroalgae surveys. During the summers of 2021 and 2022, we characterized macroalgae assemblages on subtidal rocky reefs via scuba (n = 11-16 sites per year, 3-5 per subregion). At each site, divers laid a 40 m transect along the isobath at 5-7 m depth, parallel to shore, then placed 1 m2 quadrats (n = 4-6 quadrats per site) at predetermined intervals along the transect. We collected all kelps (i.e., canopy-forming brown macroalgae in the order Laminariales) from the 1 m2 quadrat and all understory macroalgae (i.e., the diverse consortium of bladed, foliose, and filamentous seaweed taxa residing under the canopy) from a ¼ m2 area of the quadrat. In the lab, we sorted macroalgae by species, identified them to the lowest possible taxonomic level, dried them by spinning, and weighed each. We performed these surveys between July and mid-September (oceanographic summer) of both years. Fish surveys. To charac..., # Data for: Kelp forest loss and emergence of turf algae reshapes energy flow to predators in a rapidly warming ecosystem Dataset DOI: [10.5061/dryad.bcc2fqzqz](10.5061/dryad.bcc2fqzqz) ## Description of the data and file structure Our study took place in four subregions of the Maine coast that span a gradient of temperature and kelp forest habitat condition. At each study site, we conducted surveys to quantify available basal resources (macroalgae) and characterize the fish assemblage. We then collected representative primary producers and the two dominant fish species for stable isotope analysis. We analyzed these fish using both bulk tissue and compound-specific stable isotope analyses to document fish isotopic niches and energy use on kelp-dominated vs. red turf algae-dominated reefs. ## Files and variables ### File: Data1\_macroalgae\_biomass.csv **Description:** This dataset contains measurements of seaweed biomass (i.e., kelp, red macroalgae, and other seaweeds) collected ...,气候变化正在摧毁全球各地生态系统中的生境构建物种。然而，生境丧失对更广食物网的能量动态的影响，在包括冷水海带林在内的诸多标志性生态系统中仍不明确。本研究评估了缅因湾海带林消失及后续低矮垫状藻类（turf algae）的大量增殖，如何改变了礁区掠食性鱼类的营养生态位与所获取的能量。对鱼类肌肉组织的批量组织碳稳定同位素δ¹³C与氮稳定同位素δ¹⁵N分析显示，海带林内的鱼类拥有更大的营养生态位，且种间生态位分化程度高于垫状藻礁上的鱼类。此外，对必需氨基酸的δ¹³C分析表明，海带来源的能量占森林鱼类能量消耗的绝大多数（平均超过50%），而垫状藻礁上的鱼类则通过更多依赖浮游植物为基础的能量通道，以弥补海带林减少带来的能量不足。因此，生态系统向垫状藻类的状态转变——目前已是全球现象，可能产生深远影响…… ## 第一部分：水下调查 Data1_macroalgae_biomass.csv Data2_roving_fishes.csv ### 大型藻类调查 2021与2022年夏季，研究人员通过水肺潜水对潮下带岩礁的大型藻类群落进行表征（每年样点数为11-16，每个亚区域3-5个）。在每个样点，潜水员沿等深线布设一条长40m的样带，深度为5-7m，与海岸平行，随后沿样带按预定间隔放置1m²样方（每个样点放置4-6个样方）。研究人员从1m²样方中采集所有海带（即海带目（Laminariales）的褐藻造栖大型藻类），并从样方内¼m²区域采集所有底层大型藻类（即栖息于冠层下的叶片状、叶状及丝状海藻类群）。实验室中，研究人员按物种对大型藻类进行分类，鉴定至最低可行的分类阶元，经离心干燥后称重。所有调查均于两年的7月至9月中旬（海洋学定义的夏季）期间开展。 ### 鱼类调查 为表征…… # 数据集对应研究主题：海带林消失与垫状藻类兴起重塑快速变暖生态系统中捕食者的能量流动 数据集DOI：10.5061/dryad.bcc2fqzqz ## 数据与文件结构说明 本研究在缅因州海岸的四个亚区域开展，该区域涵盖温度与海带林生境状况的梯度样带。在每个研究样点，研究人员开展调查以量化可利用的基础资源（大型藻类），并表征鱼类群落。随后采集代表性初级生产者与两种优势鱼类物种，用于稳定同位素分析（stable isotope analysis）。研究人员采用批量组织分析与化合物特异性稳定同位素分析（compound-specific stable isotope analysis），分析以海带为主的礁区与以红色垫状藻类为主的礁区鱼类的同位素生态位与能量利用模式。 ## 文件与变量 ### 文件：Data1_macroalgae_biomass.csv **描述：** 本数据集包含海藻生物量（即海带、红色大型藻类及其他海藻）的测量数据，采集自……