Abstract

Cross BK, Taylor TN, Moore BC, Lanouette BP. 2021. Zooplankton and profundal macroinvertebrate responses to hypolimnetic oxygenation in North Twin Lake, Washington. Lake Reserv Manage. 37:275–288.

Hypolimnetic oxygenation (HO) has been used to address lake eutrophication and fish habitat limitations, but details on zooplankton and profundal macroinvertebrate community responses are required to fully understand the trophic linkages and impacts. Compared to adjacent South Twin Lake (an unoxygenated reference), zooplankton and profundal macroinvertebrate densities and distributions were altered by HO in North Twin Lake. Overall, temporal trends in zooplankton density were similar between lakes despite oxygenation, suggesting annual and seasonal influences remained a primary factor affecting their density trends. During the day, Chaoborus density was significantly greater in the water column of unoxygenated South Twin Lake compared to oxygenated North Twin Lake (P < 0.0001) as the oxygenated hypolimnion no longer provided refuge from fish predation. Daphnia and copepod densities were greater in North Twin Lake during oxygenation compared to South Twin Lake (P = 0.0011 and P = 0.0005), which may reflect increases in zooplankton habitat availability and reduced predation from Chaoborus in response to HO. With higher levels of dissolved oxygen near the sediment–water interface in North Twin Lake, larval Chaoborus and chironomid densities in the benthic sediments were significantly higher compared to South Twin Lake (P < 0.0001 in both cases). Vertical distribution of zooplankton likely reflected some balance between habitat availability, energetic costs, and predation risk. Lakes with different fish species assemblages may not respond similarly, so managers should reflect on lake similarities between North Twin Lake and systems they manage to understand potential effects of HO and how those effects align with management objectives.

摘要

克罗斯 BK，泰勒 TN，摩尔 BC，拉努埃特 BP。2021. 华盛顿州北双子湖浮游动物和深层大型无脊椎动物对水下氧合的反应。湖泊保护区管理。37:275-288。

Hypolimnetic 氧合 (H2O) 已被用于解决湖泊富营养化和鱼类栖息地限制，但需要详细了解浮游动物和深层大型无脊椎动物群落反应，以充分了解营养联系和影响。与相邻的南双子湖（未加氧的参考）相比，北双子湖中的 H2O 改变了浮游动物和深层大型无脊椎动物的密度和分布。总体而言，尽管有氧，湖泊之间浮游动物密度的时间趋势相似，这表明年度和季节性影响仍然是影响其密度趋势的主要因素。白天，与含氧的北双湖相比，未含氧的南双湖水体中的潮波露密度显着更高（P < 0.0001)，因为含氧水下层不再提供躲避鱼类捕食的避难所。与南双子湖相比，北双子湖的水蚤和桡足类密度在充氧期间更大（P  = 0.0011 和P  = 0.0005），这可能反映了浮游动物栖息地可用性的增加和对 H2O 的潮波捕食减少。由于北双湖沉积物-水界面附近溶解氧含量较高，底栖沉积物中潮虫幼虫和摇蚊的密度显着高于南双湖（P < 0.0001 在两种情况下）。浮游动物的垂直分布可能反映了栖息地可用性、能量成本和捕食风险之间的某种平衡。具有不同鱼类种群的湖泊可能不会做出类似的反应，因此管理人员应反思北双子湖与其管理的系统之间的湖泊相似性，以了解 H2O 的潜在影响以及这些影响如何与管理目标保持一致。