Barnas Danielle M, Zeff Maya, Silbiger Nyssa J
University of Hawai'i at Mānoa, Hawai'i Institute of Marine Biology, Kāne'ohe, HI, USA.
Department of Biology, California State University Northridge, Northridge, CA, USA.
Proc Biol Sci. 2025 Jan;292(2039):20241554. doi: 10.1098/rspb.2024.1554. Epub 2025 Jan 22.
Coral reefs experience numerous environmental gradients affecting organismal physiology and species biodiversity, which ultimately impact community metabolism. This study shows that submarine groundwater discharge (SGD), a common natural environmental gradient in coastal ecosystems associated with decreasing temperatures, salinity and pH with increasing nutrients, has both direct and indirect effects on coral reef community metabolism by altering individual growth rates and community composition. Our data revealed that SGD exposure hindered the growth of two algae, and by 67 and 200%, respectively, and one coral, by 20%. Community metabolic rates showed altered community production, respiration and calcification between naturally high and low exposure areas mostly due to differences in community identity (i.e. species composition), rather than a direct effect of SGD on physiology. Production and calcification were 1.5 and 6.5 times lower in assemblages representing high SGD communities regardless of environment. However, the compounding effect of community identity and SGD exposure on respiration resulted in the low SGD community exhibiting the highest respiration rates under higher SGD exposure. By demonstrating SGD's role in altering community composition and metabolism, this research highlights the critical need to consider compounding environmental gradients (i.e. nutrients, salinity and temperature) in the broader context of ecosystem functions.
珊瑚礁经历着众多影响生物生理和物种生物多样性的环境梯度变化，这些变化最终会影响群落代谢。本研究表明，海底地下水排放（SGD）是沿海生态系统中一种常见的自然环境梯度，随着营养物质增加，温度、盐度和pH值会降低，它通过改变个体生长速率和群落组成，对珊瑚礁群落代谢产生直接和间接影响。我们的数据显示，暴露于SGD会分别阻碍两种藻类的生长，使其生长速率降低67%和200%，还会使一种珊瑚的生长速率降低20%。群落代谢率表明，在自然高暴露区和低暴露区之间，群落的生产、呼吸和钙化作用发生了变化，这主要是由于群落特征（即物种组成）的差异，而非SGD对生理的直接影响。无论环境如何，代表高SGD群落的组合中的生产和钙化作用分别比低1.5倍和6.5倍。然而，群落特征和SGD暴露对呼吸作用的综合影响导致低SGD群落在较高SGD暴露下表现出最高的呼吸速率。通过证明SGD在改变群落组成和代谢中的作用，本研究强调了在更广泛的生态系统功能背景下考虑复合环境梯度（即营养物质、盐度和温度）的迫切需求。
