Effect of seasonality on the population density of wetland aquatic insects: A case study of the Hawr Al Azim and Shadegan wetlands, Iran

Abstract

Aim: Wetlands are extremely suitable ecosystems to assess the effect of climate change on the density of aquatic insects. This study aimed to assess the effect of seasonality on populations of aquatic insects in the Hawr Al Azim and Shadegan wetlands.

Materials and methods: The insect samplings were conducted at a large area of the Hawr Al Azim and five different sites of the Shadegan wetlands. In total, 18,534 arthropods of different life stages, including 12 orders containing 51 families, were collected and identified from the selected sites of the Shadegan and Hawr Al Azim wetlands.

Results: Results showed that the population density of wetland aquatic insects gradually increased as the average daily temperature decreased, positively increased with daily mean relative humidity and precipitation, and decreased with the mean daily evaporation between October and April. Conversely, the population density of wetland aquatic insects gradually decreased with increasing average daily temperature and reduction of the mean relative humidity and precipitation and increasing the average evaporation from April to September. When differences between the average daily and water temperatures reached minimum in April, the population density of wetland aquatic insects reached maximum and turned mainly to families that they have high level of biological indices, indicating that wetlands have clean waters around the spring. While around the autumn conversely, they mostly changed to families that they have low level of biological indices, indicating that wetlands have unclean waters.

Conclusion: The present study showed an optimum condition for the growth of insects around spring. Seasonality affects the population density of wetland aquatic insects during a year.

Keywords: change of insect population; effect of seasonality on insect population density; seasonal climate change; wetland aquatic insect.

Figure-1

Location map of the Shadegan and Hawr Al Azim wetlands and sites of insect sampling. Source adapted from A: wikipedia.org 2014, B: PCE 2002, and C: persianblog.ir 2014.

Figure-2

Meteorological data, October 2011-September 2012. MDT=Mean daily temperature, MWT=Mean water temperature, MRH=Mean relative humidity, ME=Mean evaporation, and R=Rainfall.

Figure-3

Monthly abundance of the aquatic insects in the Shadegan and Hawr Al Azim wetlands, October 2011-September 2012. SW₁ to SW₅=Selected sites of the Shadegan wetland and HH=Hawr Al Azim wetland.

Figure-4:

Monthly abundance of aquatic insect orders (suborders) in the Shadegan and Hawr Al Azim wetlands, October 2011-September 2012. Col=Coleoptera, Dip=Diptera, Ephem=Ephemeroptera, Hem=Hemiptera, Lep=Lepidoptera, Anis=Odonata: Anisoptera, Zyg=Odonata: Zygoptera, Deca=Decapoda and Mys=Mysida.

Figure-5

Differences between mean water and daily temperature of the Shadegan and Hawr Al Azim wetlands, October 2011-September 2012. SW₁ to SW₅=Selected sites of the Shadegan wetland and HH=Hawr Al Azim wetland, MDT=Mean daily temperature and MWT=Mean water temperature.