Salinization effects on coastal ecosystems: a terrestrial model ecosystem approach

Abstract

In coastal areas, intrusion/irrigation with seawater can threaten biodiversity along with crop yields, and the leaching of salts from areas affected by these processes can increase the salinity of water bodies nearby. The aims of this study were to evaluate the effects of salinization on coastal soil ecosystems due to saline intrusion/irrigation. Terrestrial model ecosystems were used to simulate two soil salinization scenarios: (i) seawater intrusion and irrigation with distilled water and (ii) seawater intrusion and irrigation with saline water. Three sampling periods were established: T0-after acclimation period; T1-salinization effects; and T2-populations' recovery. In each sampling period, the abundance of nematodes, enchytraeids, springtails, mites and earthworms, and plant biomass were measured. Immediate negative effects on enchytraeid abundance were detected, especially at the higher level of saltwater via intrusion+irrigation. Eight weeks after the cessation of saline irrigation, the abundance of enchytraeids fully recovered, and some delayed effects were observed in earthworm abundance and plant biomass, especially at the higher soil conductivity level. The observed low capacity of soil to retain salts suggests that, particularly at high soil conductivities, nearby freshwater bodies can also be endangered. Under saline conditions similar to the ones assayed, survival of some soil communities can be threatened, leading to the loss of biodiversity.This article is part of the theme issue 'Salt in freshwaters: causes, ecological consequences and future prospects'.

Keywords: climate change; intrusion; irrigation; sea-level rise; soil invertebrates.

Figure 1.

Over-time variation of the dry weight of plants and total abundance of five invertebrate groups in the control treatment (IIDW): mean (+ standard deviation) abundance of nematodes, springtails, mites, enchytraeids and earthworms, and dry weight of plants at the beginning of the test (T0), and sampling periods T1 and T2. Asterisks mean statistically different from control in T0, Generalized linear model, Gaussian family (link identity), p < 0.05.

Figure 2.

Effects of saltwater exposure on soil communities: mean abundance (+ standard deviation) of nematodes, springtails, mites, enchytraeids and earthworms, and mean dry weight of plants in the control (black bars) and both treatments (grey bars) in the first sampling period (T1). Treatment codes as in table 1. Asterisks mean statistically different from control, generalized linear model, Gaussian family (link identity), p < 0.05.

Figure 3.

Abundance of soil organisms after the recovery period, i.e. after cessation of saltwater irrigation: mean abundance (+ standard deviation) of nematodes, springtails, mites, enchytraeids and earthworms, and mean dry weight of plants in the control (black bars) and treatment SINSI (grey bars). Treatment codes as in table 1. Asterisks mean statistically different from control, generalized linear model, Gaussian family (link identity), p < 0.05.

Figure 4.

Discrimination of the delayed effects on earthworms after the cessation of saltwater irrigation: mean number (+ standard deviation) of earthworms divided into adults and juveniles and, also, juveniles in the two sampled layers of the TME (0–30 and 30–40 cm) (a); ratio between the number of individuals collected from the layers 30–40 cm and 0–30 cm (b). Treatment codes as in table 1. Asterisks mean statistically different from control, generalized linear model, Gaussian family (link identity), p < 0.05.