Optimum water depth ranges of dominant submersed macrophytes in a natural freshwater lake

<div><p>Macrophytes show a zonal distribution along the lake littoral zone because of their specific preferred water depths while the optimum growth water depths of dominant submersed macrophytes in natural lakes are not well known. We studied the seasonal biomass and frequency patterns of dominant and companion submersed macrophytes along the water depth gradient in Lake Erhai in 2013. The results showed that the species richness and community biomass showed hump-back shaped patterns along the water depth gradient both in polydominant and monodominant communities. Biomass percentage of <i>Potamogenton maackianus</i> showed a hump-back pattern while biomass percentages of <i>Ceratophyllum demersum</i> and <i>Vallisneria natans</i> appeared U-shaped patterns across the water depth gradient in polydominant communities whereas biomass percentage of <i>V</i>. <i>natans</i> increased with the water depth in monodominant communities. Dominant species demonstrated a broader distribution range of water depth than companion species. Frequency and biomass of companion species declined drastically with the water depth whereas those of dominant species showed non-linear patterns across the water depth gradient. Namely, along the water depth gradient, biomass of <i>P</i>. <i>maackianus</i> and <i>V</i>. <i>natans</i> showed hump-back patterns and biomasses of <i>C</i>. <i>demersum</i> displayed a U-shaped pattern in the polydominant communities but biomass of <i>V</i>. <i>natans</i> demonstrated a hump-back pattern in the monodominant communities; frequency of <i>P</i>. <i>maackianus</i> showed a hump-back pattern and <i>C</i>. <i>demersum</i> and <i>V</i>. <i>natans</i> maintained high frequencies in the two types of communities. We can speculate that in Lake Erhai the optimum growth water depths of <i>P</i>. <i>maackianus</i> and <i>C</i>. <i>demersum</i> in the polydominant communities are 2.5–4.5 m and 1–2 m or 5–6 m, respectively and that of <i>V</i>. <i>natans</i> is 3–5 m in the polydominant communities and 2.5–5 m in the monodominant communities. This is the first report that the optimum water depth ranges in the horizontal direction of three dominant submersed macrophytes in a natural freshwater lake were determined.</p></div

Seasonal biomass patterns of submersed species across the water depth gradient in the polydominant and monodominant communities.

<p>Seasonal biomass patterns of submersed species across the water depth gradient in the polydominant and monodominant communities.</p

Seasonal frequency patterns of submersed species across the water depth gradient in the polydominant and monodominant communities.

<p>Seasonal frequency patterns of submersed species across the water depth gradient in the polydominant and monodominant communities.</p

Relations between water depth and species richness, community biomass in the polydominant and monodominant communities.

<p>Relations between water depth and species richness, community biomass in the polydominant and monodominant communities.</p

Seasonal biomass percentages of the dominant species across the water depth gradient in the polydominant and monodominant communities.

<p>Seasonal biomass percentages of the dominant species across the water depth gradient in the polydominant and monodominant communities.</p

The minimum, maximum and range of water depth of submersed macrophytes in the polydominant and monodominant communities.

<p>CD: <i>Ceratophyllum demersum</i>; PM: <i>Potamogeton maackianus</i>; VN: <i>Vallisneria natans</i>, MS: <i>Myriophyllum spicatum</i>; HV: <i>Hydrilla verticillata</i>; PL: <i>Potamogeton lucens</i>; PA: <i>Potamogeton malaianus</i>; values shown on the top of each bar.</p