Ecological Response of Pondweeds (Potamogeton and Stuckenia) to Water Physical and Chemical Parameters in Croatia (Southeastern Europe)

Pondweeds, an important component of macrophyte vegetation, are influenced by various ecological factors of the aquatic ecosystem. In turn, pondweeds affect the nutrient and sediment dynamics and provide food and shelter for other organisms. As different species have specific environmental preferences and tolerances, they can serve as indicators of the ecological status of water bodies. Here, the ecological preference of the seven most frequent pondweeds in Croatia (<i>Potamogeton berchtoldii</i>, <i>P. crispus</i>, <i>P. lucens</i>, <i>P. natans</i>, <i>P. nodosus</i>, <i>P. perfoliatus</i> and <i>Stuckenia pectinata</i>) for chemical and physical water parameters was studied using 218 vegetation relevés and the accompanying water parameters. CCA revealed the main environmental gradients described by six parameters (chemical oxygen demand, total nitrogen, total phosphorus, electrical conductivity, dissolved oxygen and pH), while ecological responses of the species were further explored by GAMs. <i>Potamogeton berchtoldii</i>, <i>P. lucens</i>, <i>P. natans</i> and <i>P. perfoliatus</i> prefer clean, oxygenated, oligo- to mesotrophic water, and <i>P. crispus</i> and <i>S. pectinata</i> thrived in eutrophic water with low oxygen levels, while <i>P. nodosus</i> is a widespread generalist. The results of this study explain the distribution patterns of <i>Potamogeton</i> and <i>Stuckenia</i> species in Croatia, and add to the general knowledge on their role as bioindicators.