Turf algae redefine the chemical landscape of temperate reefs, limiting kelp forest recovery

In temperate regions experiencing rapid ocean warming, kelp forests are being replaced by chemically-rich turf algae. Yet, the extent to which these turf algae alter the surrounding chemical environment or impact the rebound potential of kelp forests via allelopathy remains unknown. Here, we used underwater visual surveys, comprehensive chemical profiling, and laboratory experiments to reveal that turf algae release bioactive compounds into the water that fundamentally alter the reef “chemical landscape” and directly suppress kelp recruitment. Our study, therefore, reveals that allelopathy is critical in shaping modern kelp forest ecosystems and their resilience. Further, it demonstrates that reversing climate-driven state shifts will require not only curbing global carbon emissions, but also targeted local interventions that break harmful ecological feedback loops and foster recovery., Quantifying seaweed community structure on the reef
Files
Algal_Biomass.csv
Kelp_Recruitment_Counts.csv
Turf_Cover.csv
At each site, SCUBA divers deployed a 40-meter transect on the reef, set perpendicular to shore and contouring the 5-7 m depth isobath (mean lower low water). Within replicate 1 m2 quadrats deployed at set intervals along the transect (n = 8 per site), we visually counted the number of juvenile kelp recruits. Then, in a portion (0.25 m2 area) of each quadrat, we estimated the abundance of turf algae (percent cover). To identify the species composition of the turf algae community (which can be difficult to discern underwater), we next harvested all kelps (in the 1 m2 area) and all low-lying seaweeds residing under the canopy, including bladed, foliose, and turf algae species (in the 0.25 m2 area) from a subset of quadrats (n = 4-6 per site). Collected seaweeds were kept cool on the boat and brought back to the lab within 6 hours, where they were sorted to species, spun (..., , # Turf algae redefine the chemical landscape of temperate reefs, limiting kelp forest recovery

Dataset DOI: [https://doi.org/10.5061/dryad.kd51c5bhd](https://doi.org/10.5061/dryad.kd51c5bhd)

## Description of the data and file structure

### **Algal\_Biomass.csv**

Description:

This dataset contains measurements of seaweed biomass (kelp, turf algae, and other seaweeds) collected from 1m² quadrats across six study sites over three years. (See “Quantifying seaweed community structure on the reef” in the methods section for detailed methods)

* To note for this paper \"Turf\" communities (i.e., those comprised of red, green, and/or brown filamentous and uniseriate algae, ~1 cm to ~15 cm in canopy height, that form upright filaments, mats, or tufts) can include any of the following species: *Acrosiphonia_spp, Antithamnion_spp, Antithamnionella_spp, Audouinella_spp, Bonnemaisonia_hamifera, Carradoriella_elongata, Ceramium_spp, Cladophora_spp, Dasysiphonia_japonica, Ectocarpus_spp, Kaprunia_...,

在海洋快速变暖的温带海域，海藻林正被富含化学物质的表层藻类（turf algae）所取代。然而，这类表层藻类通过化感作用（allelopathy）改变周边化学环境，或是影响海藻林恢复潜力的程度，目前仍不明晰。本研究借助水下视觉调查、全面化学谱分析（chemical profiling）与室内实验，证实表层藻类会向水体释放生物活性化合物，从根本上重塑礁体“化学景观”，并直接抑制海带幼体补充（kelp recruitment）。因此，本研究揭示化感作用在塑造现代温带海藻林生态系统及其恢复力（resilience）中发挥关键作用。进一步研究表明，逆转气候驱动的生态状态转换，不仅需要遏制全球碳排放，还需开展针对性本地干预，以打破有害生态反馈循环并促进生态恢复。

### 礁体海藻群落结构量化
#### 数据集文件
1. Algal_Biomass.csv
2. Kelp_Recruitment_Counts.csv
3. Turf_Cover.csv

在每个采样点，SCUBA潜水员（SCUBA divers）会在礁体上布置一条垂直于岸线、沿5-7米深度等深线（isobath）（平均低潮低潮位）延伸的40米样带。沿样带按固定间隔设置重复1平方米样方（每个采样点设8个样方），在样方内通过视觉计数统计幼年海带幼体补充个体的数量。随后，在每个样方的0.25平方米区域内，估算表层藻类的盖度百分比。为鉴定表层藻类群落的物种组成（水下难以直接分辨），我们从部分样方（每个采样点4-6个样方）中采集1平方米样方内的所有海带，以及冠层下的所有低矮海藻，包括片状、叶状及表层藻类物种（采样区域为0.25平方米）。采集的海藻样本在船上低温保存，并于6小时内运回实验室，随后进行物种分类、离心甩干处理……

# 表层藻类重塑温带礁体化学景观，限制海藻林恢复
数据集DOI：[https://doi.org/10.5061/dryad.kd51c5bhd](https://doi.org/10.5061/dryad.kd51c5bhd)

## 数据与文件结构说明
### **Algal_Biomass.csv**
#### 数据描述：
本数据集包含三年间6个研究站点的1平方米样方内的海藻生物量测量数据，涵盖海带、表层藻类及其他海藻。详细实验方法参见方法部分的「礁体海藻群落结构量化」。

* 研究说明：本研究中的「表层藻类（Turf）群落」指由红藻、绿藻和/或褐藻组成的丝状、单列藻类，冠层高度约1 cm至15 cm，可形成直立丝状体、垫状物或丛状结构，包含以下物种：*Acrosiphonia_spp、Antithamnion_spp、Antithamnionella_spp、Audouinella_spp、Bonnemaisonia_hamifera、Carradoriella_elongata、Ceramium_spp、Cladophora_spp、Dasysiphonia_japonica、Ectocarpus_spp、Kaprunia_……*（原文未完结）