ABSTRACT

We measured δ¹⁵N, δ¹³C, and percent carbon (C) and nitrogen (N) on foot and remaining soft tissue of the two native freshwater mussel species Echyridella aucklandica and E. menziesii (Hyriidae: Unionida) from three Waikato, northern New Zealand, streams to investigate differences among sites, sexes and species. Mean differences in δ¹⁵N and δ¹³C between foot and remaining soft tissue (mainly guts, gills and gonads) were <0.5‰, whereas %C and %N were higher in foot tissue and C:N values were lower. No differences were detected between mussel species, but δ¹⁵N and δ¹³C displayed marked differences among sites for both species, with δ¹⁵N variations consistent with the level of catchment land-use intensification. Variation in δ¹³C and δ¹⁵N among replicate mussels was low indicating few individuals are required to precisely characterise isotope signatures of local populations. The lack of evidence of trophic resource partitioning among species, and consistent differences in isotope ratios between sites, suggests that the more widespread and abundant E. menziesii may provide an effective baseline integrator of catchment activities that alter carbon supplies and nitrogen sources.

摘要

我们测量了来自北部怀卡托的三个本地淡水贻贝物种Echyridella aucklandica和E. menziesii（贻贝科：Unionida）的δ ¹⁵ N、δ ¹³ C 以及碳 (C) 和氮 (N) 百分比以及剩余软组织新西兰，河流调查地点、性别和物种之间的差异。足部和剩余软组织（主要是内脏、鳃和性腺）之间δ ¹⁵ N 和 δ ¹³ C 的平均差异<0.5‰，而足部组织中的 %C 和 %N 较高，而 C:N 值较低。贻贝物种之间没有检测到差异，但 δ ¹⁵ N 和 δ ¹³ C 在两个物种的位置之间显示出显着差异，δ¹⁵ N 变化与集水区土地利用集约化水平一致。复制贻贝中 δ ¹³ C 和 δ ¹⁵ N 的变化很小，表明需要很少的个体来精确表征当地种群的同位素特征。缺乏物种之间营养资源分配的证据，以及地点之间同位素比率的一致差异，表明更广泛和丰富的E. menziesii可能为改变碳供应和氮源的集水活动提供有效的基线整合。