Department of Biological Sciences, University of Waikato, Hamilton, New Zealand.
PLoS One. 2011;6(10):e27065. doi: 10.1371/journal.pone.0027065. Epub 2011 Oct 28.
The suspension feeding bivalve Austrovenus stutchburyi is a key species on intertidal sandflats in New Zealand, affecting the appearance and functioning of these systems, but is susceptible to several environmental stressors including sedimentation. Previous studies into the effect of this species on ecosystem function have been restricted in space and time, limiting our ability to infer the effect of habitat change on functioning. We examined the effect of Austrovenus on benthic primary production and nutrient dynamics at two sites, one sandy, the other composed of muddy-sand to determine whether sedimentary environment alters this key species' role. At each site we established large (16 m(2)) plots of two types, Austrovenus addition and removal. In winter and summer we deployed light and dark benthic chambers to quantify oxygen and nutrient fluxes and measured sediment denitrification enzyme activity to assess denitrification potential. Rates of gross primary production (GPP) and ammonium uptake were significantly increased when Austrovenus was added, relative to removed, at the sandy site (GPP, 1.5 times greater in winter and summer; ammonium uptake, 8 times greater in summer; 3-factor analysis of variance (ANOVA), p<0.05). Denitrification potential was also elevated in Austrovenus addition plots at the sandy site in summer (by 1.6 times, p<0.1). In contrast, there was no effect of Austrovenus treatment on any of these variables at the muddy-sand site, and overall rates tended to be lower at the muddy-sand site, relative to the sandy site (e.g. GPP was 2.1 to 3.4 times lower in winter and summer, respectively, p<0.001). Our results suggest that the positive effects of Austrovenus on system productivity and denitrification potential is limited at a muddy-sand site compared to a sandy site, and reveal the importance of considering sedimentary environment when examining the effect of key species on ecosystem function.
悬浮滤食性双壳类 Austrovenus stutchburyi 是新西兰潮间带沙滩上的关键物种，影响着这些系统的外观和功能，但易受到包括沉积作用在内的多种环境胁迫的影响。之前关于该物种对生态系统功能影响的研究在空间和时间上受到限制，限制了我们推断栖息地变化对功能的影响的能力。我们在两个地点（一个是沙质的，另一个是由泥质砂组成的）研究了 Austrovenus 对底栖初级生产力和营养动态的影响，以确定沉积环境是否改变了这个关键物种的作用。在每个地点，我们建立了两个类型的大（16 平方米）的实验区，即 Austrovenus 添加区和移除区。在冬季和夏季，我们部署了明暗底栖室来量化氧气和营养通量，并测量了沉积物反硝化酶活性以评估反硝化潜力。与移除区相比，在沙质地点，当 Austrovenus 添加时，总初级生产力（GPP）和铵吸收速率显著增加（冬季增加 1.5 倍，夏季增加 8 倍；3 因素方差分析（ANOVA），p<0.05）。夏季沙质地点 Austrovenus 添加区的反硝化潜力也升高（增加 1.6 倍，p<0.1）。相比之下，在泥质砂地点，Austrovenus 处理对这些变量没有影响，并且整体速率相对较低（例如，冬季和夏季的 GPP 分别低 2.1 到 3.4 倍，p<0.001）。我们的结果表明，与沙质地点相比，Austrovenus 对系统生产力和反硝化潜力的积极影响在泥质砂地点受到限制，并揭示了当检查关键物种对生态系统功能的影响时考虑沉积环境的重要性。
