Research Centre for Fisheries and Aquaculture, Institute of Aquaculture and Environmental Safety, Hungarian University of Agriculture and Life Sciences, Szarvas, 5540, Hungary.
Pál Juhász-Nagy Doctoral School of Biology and Environmental Sciences, University of Debrecen, Debrecen, 4032, Hungary.
Sci Rep. 2023 Oct 17;13(1):17691. doi: 10.1038/s41598-023-44381-3.
Although ground-baiting related nutrient loading has been widely studied, we do not know what proportion of these nutrients release into the water column, affecting primary production directly. We conducted short-term (24-h, 5-day) experiments at wide temperature range, in presence and absence of fish using fish meal-based (FM-GB) and plant-based groundbait (PB-GB), to assess the nitrogen (N) and phosphorus (P) fluxes from GB into the water column. Nitrogen release from unconsumed FM-GB was negligible in the first 3 days, then increased abruptly, releasing 32% of its total N content by the fifth day. In contrast, PB-GB acted as temporary sink for inorganic N forms. Considerable (18-21%) inorganic P release was observed in both GB types in the first twelve hours. Consumed GBs induced considerable inorganic N release and its rate increased with temperature. Particulate forms predominated the released N in PB-GB, suggesting impaired digestion. Phosphorus-dominated by particulate forms-release was similar or lower than in unconsumed GB. Based on our results, excessive use of GB-when high amount of it remains unconsumed-can enhance eutrophication in P-limited ecosystems. Although less digestible GBs may have less abrupt effect on the primary production, undigested nutrients remain unavailable for removal through fish harvest.
虽然已有大量关于诱饵投喂相关营养负荷的研究，但我们仍不清楚这些营养物质中有多大比例会释放到水柱中，从而直接影响初级生产力。我们进行了短期（24 小时、5 天）实验，在有鱼和无鱼的情况下，使用基于鱼粉的（FM-GB）和基于植物的（PB-GB）两种诱饵，评估了诱饵中氮（N）和磷（P）向水柱中的通量。在最初的 3 天内，未消耗的 FM-GB 中几乎没有氮释放，然后突然增加，在第 5 天释放了其总氮含量的 32%。相比之下，PB-GB 对无机氮形式起到了暂时的汇作用。在两种类型的诱饵中，最初 12 小时内都观察到相当数量（18-21%）的无机磷释放。消耗的诱饵会引起相当数量的无机氮释放，其释放速率随温度升高而增加。在 PB-GB 中，释放的氮主要以颗粒形式存在，这表明消化受到了损害。磷主要以颗粒形式释放，与未消耗的诱饵相似或更低。基于我们的研究结果，在磷限制的生态系统中，当大量诱饵未被消耗时，过度使用诱饵可能会加剧富营养化。虽然较难消化的诱饵可能对初级生产力的影响不那么突然，但未消化的营养物质仍无法通过鱼类收获去除。
