Temporal and Spatial Dynamics of Phytoplankton Primary Production in Lake Taihu Derived from MODIS Data

Yibo Zhang,Yunlin Zhang,Kun Shi,Yubing Deng,Deping Li

doi:10.3390/rs9030195

Abstract

We investigated the long-term variations in primary production in Lake Taihu using Moderate Resolution Imaging Spectroradiometer (MODIS) data, based on the Vertically Generalized Production Model (VGPM). We firstly test the applicability of VGPM in Lake Taihu by comparing the results between the model-derived and the in situ results, and the results showed that a strong significant correlation (R2 = 0.753, p < 0.001, n = 63). Then, VGPM was used to map temporal-spatial distributions of primary production in Lake Taihu. The annual mean daily primary production of Lake Taihu from 2003 to 2013 was 1094.06 ± 720.74 mg·C·m−2·d−1. Long-term primary production maps estimated from the MODIS data demonstrated marked temporal and spatial variations. Spatially, the primary production in bays, especially in Zhushan Bay and Meiliang Bay, was consistently higher than that in the open area of Lake Taihu, which was caused by chlorophyll-a concentrations resulting from high nutrient concentrations. Temporally, the seasonal variation of primary production from 2003 to 2013 was: summer > autumn > spring > winter, with significantly higher primary production found in summer and autumn than in winter (p < 0.005, t-test), primarily caused by seasonal variations in water temperature. On a monthly scale, the primary production exerts a clear character of bimodality, increasing from January to May, decreasing in June or July, and finally reaching its highest value during August or September. Wind is another important factor that could affect the spatial variations of primary production in the large, eutrophic and shallow Lake Taihu.

Highlights

Phytoplankton is at the bottom of the food chain, creating fresh organic matter from inorganic nutrients, carbon dioxide and energy from sunlight, which strongly influence nutrient concentrations and support higher trophic levels such as zooplankton and filter feeder
Biogeochemical parameters in Lake Taihu are always characterized by highly temporal-spatial dynamics, indicating that estimates of primary production using traditional sampling methods may lead to large uncertainty when we investigate primary production dynamics in the whole lake for a long time period
The estimated phytoplankton primary production through satellite data and in situ measured phytoplankton primary production should be consistent within a limited period

Summary

Introduction

Phytoplankton is at the bottom of the food chain, creating fresh organic matter from inorganic nutrients, carbon dioxide and energy from sunlight, which strongly influence nutrient concentrations and support higher trophic levels such as zooplankton and filter feeder. Estimation of the phytoplankton primary production is an important topic in fisheries resource management and global change [4]. One of the major goals of modern biological oceanography is to acquire a better understanding of primary production in various oceanic provinces, with a special emphasis on marine carbon cycling. As an important part of the global carbon cycle, estimating the primary production in lakes is the major goals of modern limnology, and important for us to understand the regional ecological environment [4]. Lake primary production, which is commonly regarded as the photosynthetic capacity of phytoplankton for the unit volume, is an important parameter to describe ecosystem and environmental characteristics of lake [6]

Results

Discussion

Conclusion