Horn Kali M, Fournet Michelle E H, Liautaud Kaitlin A, Morton Lynsey N, Cyr Allie M, Handley Alyse L, Dotterweich Megan M, Anderson Kyra N, Zippay Mackenzie L, Hardy Kristin M
Department of Biological Sciences, Center for Coastal Marine Sciences, California Polytechnic State University, San Luis Obispo, CA 93407, USA.
Cornell Lab of Ornithology, Cornell University, Ithaca, NY 14850, USA.
Integr Org Biol. 2021 Apr 30;3(1):obab010. doi: 10.1093/iob/obab010. eCollection 2021.
The intertidal zone is characterized by persistent, tidally-driven fluctuations in both abiotic (e.g., temperature, oxygen, and salinity) and biotic (e.g., food availability and predation) factors, which make this a physiologically challenging habitat for resident organisms. The relative magnitude and degree of variability of environmental stress differ between intertidal zones, with the most extreme physiological stress often being experienced by organisms in the high intertidal. Given that so many of the constantly shifting parameters in this habitat are primary drivers of metabolic rate (e.g., temperature, [O], and food availability), we hypothesized that sessile conspecifics residing in different tidal zones would exhibit distinct "metabolic phenotypes," a term we use to collectively describe the organisms' baseline metabolic performance and capacity. To investigate this hypothesis, we collected acorn barnacles () from low, mid, and high intertidal positions in San Luis Obispo Bay, CA, and measured a suite of biochemical (whole-animal citrate synthase (CS) and lactate dehydrogenase (LDH) activity, and aerial [D-lactate]), physiological (O consumption rates), morphological (body size), and behavioral (e.g., cirri beat frequency and percentage of time operculum open) indices of metabolism. We found tidal zone-dependent differences in metabolism that primarily related to anaerobic capacity, cirral activity patterns, and body size. Barnacles from the low intertidal tended to have a greater capacity for anaerobic metabolism (i.e., increased LDH activity and increased baseline [D-lactate]), have reduced cirral beating activity-and presumably reduced feeding-when submerged, and be smaller in size compared to conspecifics in the high intertidal. We did not, however, see any D-lactate accumulation in barnacles from any tidal height throughout 96 h of air exposure. This trend indicates that the enhanced capacity of low intertidal barnacles for anaerobic metabolism may have evolved to support metabolism during more prolonged episodes of emersion or during events other than emersion (e.g., coastal hypoxia and predation). There were also no significant differences in CS activity or baseline O consumption rates (in air or seawater at 14°C) across tidal heights, which imply that aerobic metabolic capacity may not be as sensitive to tidal position as anaerobic processes. Understanding how individuals occupying different shore heights differ in their metabolic capacity becomes increasingly interesting in the context of global climate change, given that the intertidal zone is predicted to experience even greater extremes in abiotic stress.
潮间带的特点是，非生物因素（如温度、氧气和盐度）和生物因素（如食物供应和捕食）持续受到潮汐驱动而波动，这使得该栖息地对栖息生物来说生理挑战极大。不同潮间带环境压力的相对大小和变化程度有所不同，潮间带上部的生物通常会经历最极端的生理压力。鉴于该栖息地中如此多不断变化的参数是代谢率的主要驱动因素（如温度、[氧气]和食物供应），我们推测，栖息在不同潮间带的固着同种生物会表现出不同的“代谢表型”，我们用这个术语来共同描述生物体的基础代谢性能和能力。为了验证这一假设，我们从加利福尼亚州圣路易斯奥比斯波湾的低潮、中潮和高潮间带位置采集了藤壶，并测量了一系列代谢指标，包括生化指标（全动物柠檬酸合酶（CS）和乳酸脱氢酶（LDH）活性以及空气中的[D-乳酸]）、生理指标（氧气消耗率）、形态指标（体型大小）和行为指标（如蔓足搏动频率和鳃盖打开时间百分比）。我们发现，潮间带依赖性的代谢差异主要与无氧能力、蔓足活动模式和体型大小有关。低潮间带的藤壶往往具有更强的无氧代谢能力（即LDH活性增加和基线[D-乳酸]增加），在被淹没时蔓足搏动活动减少，推测进食也减少，并且与高潮间带的同种藤壶相比体型更小。然而，在96小时的空气暴露期间，我们没有在任何潮位高度的藤壶中观察到D-乳酸积累。这种趋势表明，低潮间带藤壶增强的无氧代谢能力可能已经进化，以支持在更长时间的出露期间或出露以外的事件（如沿海缺氧和捕食）中的代谢。不同潮位高度的CS活性或基线氧气消耗率（在14°C的空气中或海水中）也没有显著差异，这意味着有氧代谢能力可能不像无氧过程那样对潮位位置敏感。鉴于预计潮间带将经历更大的非生物压力极端情况，在全球气候变化的背景下，了解占据不同海岸高度的个体在代谢能力上的差异变得越来越有趣。
