**1. Introduction**

Wetlands are sites of high biodiversity and productivity (Mitsch & Gosselink, 2000). They provide essential services, such as maintenance of atmosphere composition, key habitats for migratory species, and important nursery areas (Basset & Abbiati, 2004), but these ecosystems have suffered a serious decline worldwide due to human influence (Shine & Klemm, 1999; Solimini et al., 2008; Stenert & Maltchik, 2007). Declining water quality, drainage, eutrophication and catchment disturbances such as development, loss of natural vegetation and poor agricultural practices are changing the fundamental ecology of shallow lakes in much of the world (Drake et al., 2011). Different management strategies have been developed to solve these conservation problems, for instance the Europeans Natura 2000 network and Water Framework Directive (WFD).

Among these aquatic systems, coastal wetlands have been subject to massive environmental degradation and habitat destruction worldwide (Goudie, 1990). For example, more than 50% of the original area of coastal wetlands that existed in 1900 has been lost in most countries of Western Europe (Jones & Hughes, 1993). However, not until very recently have they become the focus of conservation interest per se (Abbiati & Basset, 2001; Barnes, 1999) with the declaration of Special Areas of Conservation as a consequence of their listing as a priority habitat type (1150\*) on Annex I of the European Union Habitats Directive (Council Directive 92/43/EEC).

Coastal lagoons constitute a common coastal environment, occupying 13% of coastal areas worldwide (Kjerfve, 1994). The conservation of these habitats depends largely on the assessment of their natural characteristics, especially biodiversity, which is one of the main criteria used when elaborating wetland protection policies (Ramsar Convention Bureau, 2005). To assess the conservation status of wetlands correctly it is necessary to include studies of the invertebrate fauna. In this sense, the composition and abundance of benthic invertebrates is one of the most important criteria to be considered. Within this group of organisms are insects, especially Coleoptera and Hemiptera, which are two of the most common groups in these environments and also two of the most important groups in the freshwater food chain.

The purpose of this chapter is to study the importance of the invertebrate fauna in the conservation of coastal lagoons and to assess the effectiveness of protecting areas on the conservation of their biological values. The questions are: "Is the Natura 2000 network

Biodiversity and Conservation of Coastal Lagoons 3

Typical lagoons are water bodies clearly separated from the sea by a sandbar, being their formation related to coastal dynamics. These ecosystems are very heterogeneous in physiography and hydrology (Ponti et al., 2011), due to the varying balance of water, salt, nutrients, particulate organic and inorganic matter (Orfanidis et al., 2008). They can receive freshwater from streams and brooks, runoff or groundwater, as well as seawater by the action of tides or waves. They are characterized by strong directional gradients of salinity, organic matter, nutrients and oxygen concentrations, which act as fine-mesh filters in

Fig. 1. The Bodeira lagoon, located in the province of Pontevedra (Northwestern Spain).

The hydrological regime is determined by the communication with the open sea and the freshwater inputs. The influence of seawater can be (1) direct through channels, being influenced by tides, or (2) by the action of storms, which makes them unpredictable systems (Casado & Montes, 1995). In this sense, one of the most important characteristics of these ecosystems is the mixture of fresh and seawater, which produces a salinity gradient. According to Kjerfve (1994) coastal lagoons can span the range of salinities from hypersaline to completely fresh. In some cases, a positive vertical gradient of salinity can exist near the outlet if the water is deep enough. This factor is one of the main conditioners of the structure and the assemblages of the communities in these aquatic systems, as well as in the

Their depth varies, although it does not exceed the 11 m. (Soria & Sahuquillo, 2009). They are generally shallow, with a high relation between surface and volume. Slope is usually little and the coastal zone is wide, so in many cases all the basin can be considered coastal.

selecting potential colonizer species (Basset, 2007).

development of many species.

effective in protecting wildlife?" and "Are Coleoptera and Hemiptera assemblages good indicators of the environmental quality of coastal lagoons?" The chapter proceeds with some definitions of "lagoons", and the characterization of the ecology and description of its biological values. Next there is a brief summary of the conservation status of these assemblages within a case study area: coastal lagoons in the Autonomous Region of Galicia, in North-western Spain. The chapter presents results from studies conducted in two periods of time separated by 10 years: 1998 and 2008. The objective was to determine whether the invertebrate fauna has changed in that period and if so, what factors are responsible for that change. The three studied lagoons are catalogued as Special Areas of Conservation (SAC) under the European Union Habitats Directive and two of them are also protected by the Ramsar Agreement. To complement the biological data, several abiotic variables were recorded at the same time as fauna was sampled. The data corresponding to 1998 had already been published in Garrido & Munilla (2008).

The areas where these lagoons are located had suffered an increasing anthropogenic impact in recent years, mainly due to the expansion of tourist areas. Thus it is important to know if the protection figures are effective in the conservation of species and environments. The analysis of the data has allowed us to know the conservation state of the fauna and thus to assess the environmental health of these ecosystems.

#### **2. Definition and characteristics of coastal lagoons**

According to the *Interpretation Manual of European Union Habitats* (EUR April 25th, 2003), lagoons are expanses of shallow coastal salt water, of varying salinity and water volume, wholly or partially separated from the sea by sand banks or shingle, or, less frequently, by rocks. Salinity may vary from brackish water to hypersalinity depending on rainfall, evaporation and through the addition of fresh seawater from storms, temporary flooding of the sea in winter or tidal exchange.

Coastal lagoons are ecotones between terrestrial, freshwater and marine ecosystems (Basset & Abbiati, 2004). Sometimes they are mistaken for other coastal inland aquatic ecosystems, such as salt marshes and estuaries (Esteves et al., 2008). Kjerfve (1994) proposed a definition of coastal lagoons that differentiates them from other similar habitat types: an inland water body, usually oriented parallel to the coast, separated from the ocean by a barrier, connected to the ocean by one or more restricted inlets, and having depths which seldom exceed a couple of meters. A lagoon may or may not be subject to tidal mixing, and salinity can vary from that of a coastal fresh-water lake to a hypersaline lagoon, depending on the hydrologic balance. Lagoons formed as a result of rising sea level during the Holocene or Pleistocene and the building of coastal barriers by marine processes. A lagoon evolves from an estuary valley or shallow open embayment to a partially enclosed barrier-lagoon system, and then, with progressive infilling, to a marsh or deltaic-filled lagoon, ending the cycle with a depositional plain or with an eventual destruction by marine erosion (Nichols, 1989).

So, coastal lagoons can be distinguished according to several characteristics: they are close to the coastline, normally closer than one kilometre; they are not completely open to the sea; during the low tide they preserve part of the water isolated from the sea; the water body is separated from the sea and not completely surrounded by dunes; the vegetation does not cover all the wetland surface, leaving open water without submerged vegetation (Soria & Sahuquillo, 2009). Generally speaking, lagoons undergo some important temporal and spatial changes in their abiotic and biological characteristics. These abiotic gradients determine the structure of the biological assemblages (Kjerfve, 1994).

effective in protecting wildlife?" and "Are Coleoptera and Hemiptera assemblages good indicators of the environmental quality of coastal lagoons?" The chapter proceeds with some definitions of "lagoons", and the characterization of the ecology and description of its biological values. Next there is a brief summary of the conservation status of these assemblages within a case study area: coastal lagoons in the Autonomous Region of Galicia, in North-western Spain. The chapter presents results from studies conducted in two periods of time separated by 10 years: 1998 and 2008. The objective was to determine whether the invertebrate fauna has changed in that period and if so, what factors are responsible for that change. The three studied lagoons are catalogued as Special Areas of Conservation (SAC) under the European Union Habitats Directive and two of them are also protected by the Ramsar Agreement. To complement the biological data, several abiotic variables were recorded at the same time as fauna was sampled. The data corresponding to 1998 had

The areas where these lagoons are located had suffered an increasing anthropogenic impact in recent years, mainly due to the expansion of tourist areas. Thus it is important to know if the protection figures are effective in the conservation of species and environments. The analysis of the data has allowed us to know the conservation state of the fauna and thus to

According to the *Interpretation Manual of European Union Habitats* (EUR April 25th, 2003), lagoons are expanses of shallow coastal salt water, of varying salinity and water volume, wholly or partially separated from the sea by sand banks or shingle, or, less frequently, by rocks. Salinity may vary from brackish water to hypersalinity depending on rainfall, evaporation and through the addition of fresh seawater from storms, temporary flooding of

Coastal lagoons are ecotones between terrestrial, freshwater and marine ecosystems (Basset & Abbiati, 2004). Sometimes they are mistaken for other coastal inland aquatic ecosystems, such as salt marshes and estuaries (Esteves et al., 2008). Kjerfve (1994) proposed a definition of coastal lagoons that differentiates them from other similar habitat types: an inland water body, usually oriented parallel to the coast, separated from the ocean by a barrier, connected to the ocean by one or more restricted inlets, and having depths which seldom exceed a couple of meters. A lagoon may or may not be subject to tidal mixing, and salinity can vary from that of a coastal fresh-water lake to a hypersaline lagoon, depending on the hydrologic balance. Lagoons formed as a result of rising sea level during the Holocene or Pleistocene and the building of coastal barriers by marine processes. A lagoon evolves from an estuary valley or shallow open embayment to a partially enclosed barrier-lagoon system, and then, with progressive infilling, to a marsh or deltaic-filled lagoon, ending the cycle with a

depositional plain or with an eventual destruction by marine erosion (Nichols, 1989).

determine the structure of the biological assemblages (Kjerfve, 1994).

So, coastal lagoons can be distinguished according to several characteristics: they are close to the coastline, normally closer than one kilometre; they are not completely open to the sea; during the low tide they preserve part of the water isolated from the sea; the water body is separated from the sea and not completely surrounded by dunes; the vegetation does not cover all the wetland surface, leaving open water without submerged vegetation (Soria & Sahuquillo, 2009). Generally speaking, lagoons undergo some important temporal and spatial changes in their abiotic and biological characteristics. These abiotic gradients

already been published in Garrido & Munilla (2008).

assess the environmental health of these ecosystems.

the sea in winter or tidal exchange.

**2. Definition and characteristics of coastal lagoons** 

Typical lagoons are water bodies clearly separated from the sea by a sandbar, being their formation related to coastal dynamics. These ecosystems are very heterogeneous in physiography and hydrology (Ponti et al., 2011), due to the varying balance of water, salt, nutrients, particulate organic and inorganic matter (Orfanidis et al., 2008). They can receive freshwater from streams and brooks, runoff or groundwater, as well as seawater by the action of tides or waves. They are characterized by strong directional gradients of salinity, organic matter, nutrients and oxygen concentrations, which act as fine-mesh filters in selecting potential colonizer species (Basset, 2007).

Fig. 1. The Bodeira lagoon, located in the province of Pontevedra (Northwestern Spain).

The hydrological regime is determined by the communication with the open sea and the freshwater inputs. The influence of seawater can be (1) direct through channels, being influenced by tides, or (2) by the action of storms, which makes them unpredictable systems (Casado & Montes, 1995). In this sense, one of the most important characteristics of these ecosystems is the mixture of fresh and seawater, which produces a salinity gradient. According to Kjerfve (1994) coastal lagoons can span the range of salinities from hypersaline to completely fresh. In some cases, a positive vertical gradient of salinity can exist near the outlet if the water is deep enough. This factor is one of the main conditioners of the structure and the assemblages of the communities in these aquatic systems, as well as in the development of many species.

Their depth varies, although it does not exceed the 11 m. (Soria & Sahuquillo, 2009). They are generally shallow, with a high relation between surface and volume. Slope is usually little and the coastal zone is wide, so in many cases all the basin can be considered coastal.

Biodiversity and Conservation of Coastal Lagoons 5

can have a negative contribution to the productivity in most shallow lakes, because they influence water exchange with the offshore area, reducing water movement and increasing

Fig. 2. Proliferation of the water lily (*Nymphaea alba*) in the Xuño lagoon (A Coruña,

The microbial community is composed of common heterotrophic taxa of natural waters, the presence of coliforms in habitats suffering from human impact being of special interest (Soria & Sahuquillo, 2009). The bacterial community is basic in the energy flows, because it decomposes and remineralizates organic matter. The hydrology of the lagoon (freshwater or marine inputs) greatly influences the bacterial composition (Piccini & Conde, 2004). Changes in the ecosystem functioning can change the composition of the bacterial assemblages as an

Phytoplankton in coastal lagoons is rich and diverse (Ramil et al., 2007), and as primary producers are an important part of the food web in freshwater environments. Phytoplankton is usually composed of diatoms, dinoflagellates, chlorophytes, cryptophytes and other microflagellates. In the coastal lagoons it is often responsible for the eutrophication phenomenon, with dominance of phytoplankton over other groups of

Zooplankton consists of heterotrophs that live suspended in the water column, and includes protists (flagellates and ciliates) and micro animals, mainly rotifers and microcrustaceans (cladocerans, copepods and ostracods). Overall, the plankton is consumed by fish,

macroinvertebrates and some waterfowl, especially in brackish systems.

sedimentation rates (Arocena, 2007).

Northwestern Spain).

organisms.

answer to the stress factor (Langenheder et al., 2003).

Proximity to the sea makes wind exposure a greater factor than for other inland aquatic ecosystems, resulting in an important effect of vertical mixing and sediment mobilization (Kirk & Lauder, 2000). Primary production is evenly distributed throughout the lagoon without evident depth gradient, except in some special cases where there is a major presence of floating algae.

The organic matter of a lagoon comes from external inputs (runoff or pollution) and the degradation of the autochthonous organic matter. Mineralization of the organic matter can influence the oxygen balance negatively, and excessive inputs of nutrients can result in the eutrophication of the wetland. High levels of organic material cause a decrease in species diversity (Zaldívar et al., 2008).

Lagoons contain quaternary soils formed by the overflow of streams riverbeds. In many instances the action of the vegetation, especially helophytes, leads to the formation of peaty soils. Where the marine influence is greater than the continental input, sandy sediments carried by the wind are frequent. Their relatively low depth and the inputs make filling rates generally high, but these rates vary with the location, because each lagoon differs with respect to freshwater inflow, sediment input, tidal conditions and geomorphic characteristics (Nichols & Allen, 1981). Terrestrial inputs of sediments in the shallowest areas with small slopes reduce the depth and change the physiographical characteristics, which can affect the structure of biological assemblages. This phenomenon depends on the water recharge of the lagoon, the movements of the dunes or the accumulation of the vegetation.

Due to their special situation at the end of a basin, their transitional character (between continental and marine environments), and the interaction with the terrestrial ecosystem, coastal lagoons are high productivity areas (Basset, 2007; Basset et al., 2006a; Esteves et al., 2008; Kjerfve, 1994), but very unstable systems that tend to disappear due to the filling of the basin (Casado & Montes, 1995; Soria & Sahuquillo, 2009). On a geologic time scale, they are short-lived landscape features, in which the environmental transition is geologically rapid and can occur within decades to centuries (Kjerfve & Magill, 1989; Ward & Ashley, 1989).
