Data from: Year-long monitoring of physico-chemical and biological variables provide a comparative baseline of coral reef functioning in the central Red Sea

Coral reefs in the central Red Sea are sparsely studied and in situ data on physico-chemical and key biotic variables are missing to provide an important comparative baseline. To fill this gap, we monitored three reefs along a cross-shelf gradient during a full year, simultaneously collecting data on currents, temperature, salinity, dissolved oxygen (DO), chlorophyll-a, turbidity, inorganic nutrients, sedimentation, bacterial communities of reef water, and bacterial and algal composition of epilithic biofilms. Some of these environmental parameters resemble projected ‘future ocean’ conditions. Summer temperatures (29 - 33 °C) and salinity levels (39 PSU) exceeded average maxima for coral reefs globally, while DO levels were comparably low (2 - 4 mg L-1). Reef environments were highly variable over time and between reefs. Temperature and salinity differences were most pronounced between seasons. Conversely, DO, chlorophyll-a, turbidity, and sedimentation varied strongest between reefs. Similarly, biotic communities were highly dynamic between reefs and seasons. Differences in bacterial biofilms were driven by differentially abundant bacterial taxa that belonged to the families Rhodobacteraceae, Flavobacteriaceae, Flammeovirgaceae, and Pseudanabaenaceae. In algal biofilms, green crusts, brown crusts, and crustose coralline algae were most abundant and accounted for most of the variability of the communities. Higher bacterial diversity of biofilms coincided with increased algal cover during spring and summer. We identified temperature, salinity, DO, and chlorophyll-a as the physico-chemical drivers of biotic community structures by multivariate matching. These parameters are forecasted to change most with the progression of global warming and increased nutrient input, which also suggests an immediate bottom-up effect on Red Sea benthic communities as a result of climate change and anthropogenic influence. In conclusion, our study presents foundation data to provide a comparative baseline to support coral reef studies in the region and to gain insight into coral reef functioning in the Red Sea.红海中部珊瑚礁的相关研究较为匮乏，且缺乏理化与关键生物变量的原位观测数据，无法为该领域研究提供重要的对比基准。为填补这一研究空白，本研究于一整年周期内，沿跨陆架梯度对三处珊瑚礁开展长期监测，同步采集了海流、水温、盐度、溶解氧（dissolved oxygen, DO）、叶绿素a、浊度、无机营养盐、沉积速率、礁水细菌群落，以及石表生物膜的细菌与藻类组成等数据。其中部分环境参数与预测的“未来海洋”环境条件高度相似。夏季水温（29~33 ℃）与盐度（39 PSU）均超过全球珊瑚礁的平均最高值，而溶解氧浓度则相对偏低（2~4 mg·L⁻¹）。珊瑚礁环境随时间推移以及不同礁体之间均存在显著异质性：季节差异对水温与盐度的影响最为显著；反之，不同礁体间的溶解氧、叶绿素a、浊度及沉积速率的变化幅度最大。同理，生物群落在不同礁体与季节间也呈现出高度的动态变化特征。石表生物膜的细菌群落差异，主要由丰度存在显著差异的细菌类群驱动，这些类群隶属于红杆菌科（Rhodobacteraceae）、黄杆菌科（Flavobacteriaceae）、焰杆菌科（Flammeovirgaceae）以及假鱼腥藻科（Pseudanabaenaceae）。在藻类生物膜中，绿色结壳、棕色结壳以及壳状珊瑚藻的丰度最高，其变异程度主导了整个藻类群落的整体变异性。在春季与夏季，生物膜的细菌多样性升高与藻类盖度增加呈现显著的正相关关系。通过多元匹配分析，本研究确定水温、盐度、溶解氧与叶绿素a是驱动生物群落结构形成的关键理化因子。随着全球变暖进程加剧与营养盐输入增加，这些参数预计将发生最为显著的变化，这也表明气候变化与人为活动将对红海底栖生物群落产生直接的上行调控效应。综上，本研究提供的基础数据可构建对比基准，用于支撑该区域珊瑚礁相关研究，并助力解析红海珊瑚礁的生态功能机制。