Restoration of two small Mediterranean lagoons: The dynamics of submerged macrophytes and factors that affect the success of revegetation

• Published in: Ecological engineering 2013-05, Vol.54, p.1-15
• Main Authors: Rodrigo, María A., Rojo, Carmen, Alonso-Guillén, José L., Vera, Pablo
• Format: Article
• Language: English
• Subjects: Animal, plant and microbial ecology; Applied ecology; Biological and medical sciences; biomass; Cambaridae; carp; Ceratophyllum demersum; Chara; coasts; cold season; Conservation, protection and management of environment and wildlife; Crayfish; Environmental degradation: ecosystems survey and restoration; epiphytes; Exclosures experiment; fauna; Fish; Fish disturbance; Freshwater; Fundamental and applied biological sciences. Psychology; grazing; herbivores; hydrochemistry; Lagoons; land restoration; Macrophyte germination; Macrophyte re-establishment; macrophytes; Myriophyllum spicatum; Nitella; Nitella hyalina; nitrogen content; nutrient content; Oryza sativa; paddies; periphyton; phytoplankton; planting; Potamogeton; Potamogeton pectinatus; Ranunculus peltatus; Rice; seasonal variation; Sediments; Seed bank; seed germination; Seeds; shade; spring; Stuckenia pectinata; Submerged; tissues; Transformed rice field; Vegetation; vegetation cover; waterfowl; Waterfowl grazing; Zannichellia
• ISSN: 0925-8574; 1872-6992
• DOI: 10.1016/j.ecoleng.2013.01.022

Two small, shallow lagoons newly created from former rice fields in the Mediterranean coast (Albufera de València Natural Park, Spain) were restored by planting several species of submerged macrophytes (Myriophyllum spicatum, Ceratophyllum demersum, Potamogeton spp., Zannichellia peltata and Ranunculus peltatus) in 2008. Charophytes also appeared spontaneously. M. spicatum was the species that dominated both lagoons and almost completely covered their surface. M. spicatum reached a high biomass and displayed a seasonal pattern, declining during the cold season and reappearing in the spring. No submerged vegetation was observed in the lagoons from 2011 onward. The major purpose of the present study was to elucidate the factors that caused the total disappearance and prevented the regeneration of submerged vegetation cover in both lagoons. Such factors may include negative biotic relationships such as those related to the presence of fish and crayfish, waterfowl grazing, phytoplankton and epiphytic development that causes shading and abiotic factors such as water nutrient concentration. Three different types (treatments) of 1-m2 exclosures were set up and planted with macrophyte cultures that formed 3 different assemblages: Chara hispida alone, a mixture of C. vulgaris, C. baltica and Nitella hyalina and a mixture of higher plants (M. spicatum, C. demersum and Potamogeton pectinatus). The “Open” type of exclosure permitted the entrance of fish, crayfish, and birds. The “Lateral” exclosure prevented the entry of fish. The “Closed” exclosure also prevented bird grazing. To determine the potential of the seed sediment bank to regenerate submerged vegetation, we investigated lagoon sediments (i) to quantify seeds and (ii) to examine seed germination. The results indicate that there is not a sufficiently large reservoir of phanerogam seeds in the lagoon sediments to recover vegetation by germination. The “Closed” exclosures allowed the growth of all species in spite of the intense development of periphyton on macrophyte tissues and filamentous algae, which reduced light availability by up to 45%. The “Lateral” exclosures had a lower development of macrophytes. In the “Open” exclosures, almost no macrophytes were detected 3 weeks after planting. Water chemistry (P and N content) did not limit the development of the tested macrophyte species but did appear to negatively affect charophytes in one of the lagoons. The deleterious effect of exotic fauna (particularly c