Elsevier

Aquatic Botany

Volume 162, March 2020, 103209
Aquatic Botany

Variations in aquatic macrophyte phenology across three temperate lakes in the Coeur d’Alene Basin

https://doi.org/10.1016/j.aquabot.2020.103209Get rights and content

Highlights

  • Light, temperature, and hydrologic connectivity shaped macrophyte phenology.

  • Maximum biomass and senescence timing was primarily driven by dominant species.

  • Seasonal changes in sonar biovolume matched changes in macrophyte biomass.

  • The strength in the relationship between biovolume and biomass was site dependent.

  • Biovolume revealed spatially uneven changes in macrophytes over the growing season.

Abstract

We studied the phenology of submerged macrophytes within three temperate lakes in 2017. Phenology was examined with macrophyte biomass, sonar biovolume, and water quality data. The primary objective was to determine the timing and duration of macrophyte senescence. The secondary objective was to investigate the feasibility of using sonar biovolume to measure seasonal changes in macrophytes. Our results indicated that Black and Thompson lakes had longer growing seasons and higher species richness than Chatcolet Lake likely due to differences in hydrologic connectivity. Macrophyte senescence was more distinct in Black and Chatcolet lakes. The prolonged and indistinct senescence at Thompson Lake was likely due to the dominance of the macrophyte community by Myriophyllum spicatum. Biovolume results revealed complex spatial patterns in macrophyte senescence at Chatcolet Lake. Macrophyte biovolume was positively correlated with biomass at all sites. Spearman’s rank correlation was highest at Chatcolet Lake (⍴ = 0.75, p-value < 0.001) followed by Black Lake (⍴ = 0.59, p-value < 0.001) and Thompson Lake (⍴ = 0.49, p-value < 0.001). The relationship between biovolume and biomass is likely non-linear and variation in the relationship can be attributed to site specific differences such as species composition in addition to sampling error. Sonar biovolume provided a convenient and nondestructive way to measure seasonal changes in macrophytes.

Introduction

Aquatic macrophytes occupy an important place in shallow lentic ecosystems by providing numerous ecological services including fixing carbon, providing habitat and food to resident organisms, linking nutrient cycling between sediments and open water, favoring clear water states over algal turbid states through stabilization of sediments, nutrients, and algal allelopathy (Jeppesen et al., 1998). The role of macrophytes linking elements within sediments to the open water is of particular interest in the Coeur d’Alene Basin given that large portions of the Basin have been contaminated with mine tailings including high concentrations of lead, zinc, arsenic, and cadmium (Bookstrom et al., 2013; National Research Council, 2005). Macrophytes are known to absorb metals from contaminated sediments during the growing season and then release them back into the environment upon senescence (Jackson, 1998; Weis and Weis, 2004).

Examining growth patterns, especially senescence of macrophyte communities in the Basin is an important component to understanding ecosystem wide metals cycling patterns. As such, the primary objective of this study was to determine the timing and duration of submerged macrophyte senescence among three temperate lakes located in the Basin. The secondary objective of this study was to investigate the feasibility of using a consumer grade hydroacoustic system (sonar) to measure seasonal change in macrophytes. Traditional macrophyte sampling techniques such as biomass or percentage cover can be time consuming as well as destructive and require expensive laboratory work (Radomski and Holbrook, 2015; Valley et al., 2015). The collection of biovolume via sonar technology is a relatively new method to examine macrophyte variability (Duarte, 1987; Howell and Richardson, 2019; Valley et al., 2015), and if applicable in the Basin, could provide an efficient way to measure variability in macrophyte biomass across large areas.

Section snippets

Study location

A sub-basin of the Columbia River, the Coeur d’Alene Basin ranges in elevation from 1460 m in the headwaters to 649 m at the Coeur d’Alene Lake surface National Research Council, 2005. The Basin spans 3800 km2 and is often characterized in three distinct areas, the upper, middle, and lower Basins. The upper Basin drains into the middle Basin at the confluence of the North and South Forks of the Coeur d’Alene River. Downstream from this site, the middle Basin enters the lower reaches of the

Dissolved oxygen and pH

We highlight mean dissolved oxygen and pH recorded between 0.5 m and 2 m from each lake. At Black Lake, dissolved oxygen saturation was highest on June 27 at 141 % and lowest on October 3 at 78 %. Dissolved oxygen saturation at Chatcolet Lake reached its highest value on July 27 at 127 % and lowest value on September 6 at 87 %. At Thompson Lake, dissolved oxygen minimum and maximum saturations occurred at the same time as Black Lake reaching a high on June 27 at 105 % and a low on October 3 at

Influence of ecological factors on species composition and richness

Differences in light availability and temperature likely contributed to the observed contrasts in species composition. The growing season at Chatcolet Lake was approximately three weeks behind the other sites. In addition to a shorter and later growing season, Chatcolet Lake generally had higher water clarity as indicated by mean Kd, Secchi depths, and maximum macrophyte colonization depths. Contrasts in physical and chemical conditions at Thompson and Black lakes relative to Chatcolet Lake

Conclusions

Differences in light availability, water temperature, and hydrologic connectivity likely contributed to contrasts in macrophyte biomass, biovolume, and species composition across sites. Maximum biomass and senescence timing differed substantially between sites and was likely driven by the characteristics of the dominant species as well as site-specific ecological factors. Biovolume time series indicated unique fine scale spatial differences in senescence that would be difficult to observe with

Funding

This research was supported by NSF-IGERTaward #1249400 and the Coeur d’Alene Tribe Lake Management Department.

Declarations of interest

None.

CRediT authorship contribution statement

Kathleen Torso: Writing - original draft, Data curation, Formal analysis. Ben D. Scofield: Supervision, Writing - review & editing, Writing - original draft, Methodology, Formal analysis, Resources, Funding acquisition. Dale W. Chess: Supervision, Writing - review & editing.

Acknowledgments

This research study would not have been possible without support from the Coeur d’Alene Tribe. We also would like to acknowledge the anonymous reviewers for their insightful comments, which greatly improved the paper. Additionally, we would like to thank Avista Corporation for their support of aquatic macrophyte monitoring in the Coeur d’Alene Lake Basin.

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