ABSTRACT

The nutrients imported by breeding waterbirds should be considered when identifying the main sources of nutrient input to lakes. Lake Lesser Prespa (Greece), including the adjacent Vromolimni pond, hosts numerous protected waterbirds that nest in densely populated colonies across the reedbeds. The accelerated eutrophication of the lake in recent years has been of increasing concern. In addition to likely large sources of nutrients (i.e., anthropogenic activities, especially agriculture), nutrient input via waterbird excrement may further trigger eutrophication. We estimated the annual phosphorus (P) and nitrogen (N) input by the most abundant colonial-nesting waterbirds (great white pelican, Dalmatian pelican, great cormorant, and pygmy cormorant) into the lake and investigated their influence on water and sediment quality. Near the waterbird colonies, soluble nutrient concentrations in the lake sediments were higher, and chlorophyll measurements indicated higher algal growth near these sites in summer. Stable isotope analysis suggests that near the colonies, waterbirds are responsible for nutrient loadings that affect the lake sediment. The estimated N and P nutrient input into the lake by both pelican and cormorant species is at least 1243 and 1649 kg/yr, respectively. On a landscape scale, this level of loading could be of minor importance for the lake because N and P can reach 32.8 (SD 9.3) and 38.9 (5.8) mg/m² per year, respectively. Locally, however, this level of loading might induce cyanobacterial blooms, illustrated by the analysis of isolated Vromolimni pond near the lake. Our findings emphasize the likely importance of nutrient loading by waterbirds for the lake system.

摘要

在确定湖泊养分输入的主要来源时，应考虑养殖水鸟输入的养分。小普雷斯帕湖（希腊），包括毗邻的 Vromolimni 池塘，栖息着众多受保护的水鸟，它们在芦苇丛中人口稠密的群落中筑巢。近年来，湖泊的加速富营养化越来越受到关注。除了可能的大量养分来源（即人为活动，尤其是农业）外，通过水鸟排泄物输入的养分可能会进一步引发富营养化。我们估计了最丰富的群居筑巢水鸟（大白鹈鹕、达尔马提亚鹈鹕、大鸬鹚和侏儒鸬鹚）每年向湖中输入的磷 (P) 和氮 (N)，并调查了它们对水和沉积物质量的影响。在水鸟群附近，湖泊沉积物中的可溶性营养物浓度较高，叶绿素测量表明夏季这些地点附近藻类生长较高。稳定同位素分析表明，在殖民地附近，水鸟负责影响湖泊沉积物的营养负荷。估计鹈鹕和鸬鹚物种向湖中输入的 N 和 P 养分分别至少为 1243 和 1649 公斤/年。在景观尺度上，这种负荷水平对湖泊可能不太重要，因为 N 和 P 可以达到 32.8 (SD 9.3) 和 38.9 (5.8) mg/m 水鸟负责影响湖泊沉积物的营养负荷。估计鹈鹕和鸬鹚物种向湖中输入的 N 和 P 养分分别至少为 1243 和 1649 公斤/年。在景观尺度上，这种负荷水平对湖泊可能不太重要，因为 N 和 P 可以达到 32.8 (SD 9.3) 和 38.9 (5.8) mg/m 水鸟负责影响湖泊沉积物的营养负荷。估计鹈鹕和鸬鹚物种向湖中输入的 N 和 P 养分分别至少为 1243 和 1649 公斤/年。在景观尺度上，这种负荷水平对湖泊可能不太重要，因为 N 和 P 可以达到 32.8 (SD 9.3) 和 38.9 (5.8) mg/m每年²次。然而，在当地，这种负载水平可能会导致蓝藻大量繁殖，对湖附近孤立的 Vromolimni 池塘的分析说明了这一点。我们的研究结果强调了水鸟对湖泊系统营养负荷的可能重要性。