Spatial distribution and temporal variation of microcrustaceans assembly (Cladocera and Copepoda) in different compartments of a reservoir in the brazilian semiarid region

Abstract Aim: The objective of this study was to investigate the spatial and temporal variation of microcrustacean assemblages of a reservoir in the Brazilian semiarid region. Methods Physical and chemical water variables and samples of microcrustaceans were collected at eight sites of the reservoir between July 2013 and November 2014, in a total of seven campaigns. For this study, the reservoir was categorized in two compartments: lateral and central. Results Limnological variables showed significant temporal variation (PERMANOVA, Pseudo-F = 19.51, p = 0.001). Higher turbidity values and suspended solids were observed in the rainiest months, while during the dry months, we measured higher values of transparency, dissolved oxygen, and chlorophyll-a. It was not found significant spatial variation of limnological variables (PERMANOVA, Pseudo-F = 0.96; p = 0.394). During the study period, ten species were recorded: four Cladocera (Ceriodaphnia cornuta, Daphnia gessneri, Diaphanosoma birgei and Diaphanosoma spinulosum ) three Copepoda Calanoida (Argyrodiaptomus azevedoi, Notodiaptomus cearensis and Notodiaptomus iheringi) and three Copepoda Cyclopoida (Macrocyclops albidus, Thermocyclops minutus and Thermocyclops decipiens). The microcrustacean assemblages showed significant temporal variation (PERMANOVA, Pseudo-F = 4.34; p = 0.001) as well as significant spatial variation (PERMANOVA, Pseudo-F = 9.46; p = 0.001). The highest values of abundance and richness were observed in the lateral compartment, this result is mainly related to the presence of aquatic macrophytes in this region, because the analysis of partial RDA indicated that limnological variables explained only 11% of this variation (Pseudo-F = 2.08, p = 0.001). Conclusions The results suggest that the seasonality of the semiarid is an important factor in the temporal dynamics of the limnological variables, while the aquatic macrophytes play an important role in the spatial distribution of the microcrustacean assembly.

摘要

研究目的：本研究旨在探究巴西半干旱地区某水库的微型甲壳动物群落的时空变化规律。

研究方法：2013年7月至2014年11月期间，于该水库的8个采样点共开展7次采样工作，收集水体理化指标与微型甲壳动物样本。本研究将该水库划分为两个分区：沿岸分区与中心分区。

研究结果：湖沼学指标呈现显著的时间变化（置换多元方差分析，PERMANOVA，Pseudo-F=19.51，p=0.001）。多雨月份的水体浊度与悬浮固体含量更高，而旱季的水体透明度、溶解氧及叶绿素a含量则处于较高水平。湖沼学指标未表现出显著的空间差异（置换多元方差分析，PERMANOVA，Pseudo-F=0.96，p=0.394）。
本研究期间共记录10个物种：枝角类（Cladocera）4种——角突网纹溞（*Ceriodaphnia cornuta*）、格氏溞（*Daphnia gessneri*）、伯奇透明溞（*Diaphanosoma birgei*）与棘刺透明溞（*Diaphanosoma spinulosum*）；桡足类哲水蚤目（Copepoda Calanoida）3种——阿氏银镖水蚤（*Argyrodiaptomus azevedoi*）、塞阿拉诺迪镖水蚤（*Notodiaptomus cearensis*）与伊赫林诺迪镖水蚤（*Notodiaptomus iheringi*）；桡足类剑水蚤目（Copepoda Cyclopoida）3种——白色大剑水蚤（*Macrocyclops albidus*）、微小温剑水蚤（*Thermocyclops minutus*）与迷惑温剑水蚤（*Thermocyclops decipiens*）。
微型甲壳动物群落呈现显著的时间变化（置换多元方差分析，PERMANOVA，Pseudo-F=4.34，p=0.001），同时也存在显著的空间差异（置换多元方差分析，PERMANOVA，Pseudo-F=9.46，p=0.001）。沿岸分区的群落丰度与物种丰富度最高，该结果主要与该区域水生维管植物的存在相关；偏冗余分析（partial RDA）结果显示，湖沼学指标仅能解释11%的群落变异（Pseudo-F=2.08，p=0.001）。

研究结论：本研究结果表明，半干旱地区的季节节律是驱动湖沼学指标时间动态的关键因素，而水生维管植物则对微型甲壳动物群落的空间分布具有重要调控作用。