Effects of plant diversity on primary production and species interactions in brackish water angiosperm communities

Abstract

Research on plant biodiversity and ecosystem functioning has mainly focused on terrestrial ecosystems, and our understanding of how plant species diversity and interactions affect processes in marine ecosystems is still limited. To investigate if plant species richness and composition influence plant productivity in brackish water angiosperm communities, a 14 wk field experiment was conducted. Using a replacement design with a standardized initial aboveground biomass, shoots of Zostera marina, Potamogeton filiformis and P. perfoliatus were planted on a shallow, sandy bottom in replicated monocultures and all possible species combinations. Response variables included aboveground and belowground biomass, shoot density, space occupation and porewater nutrients. To determine whether selection and/or complementarity controlled productivity, additive partitioning and D i were calculated. Richness effects were species-specific and only increased the biomass production of P. perfoliatus and tuber production of P. filiformis, while species composition generally had a stronger effect on biomass production. Additive partitioning indicated a positive complementarity effect for the aboveground biomass production in bicultures in general, while a positive net effect was found in the P. perfoliatus and P. filiformis biculture. Despite the absence of significant results for other treatments and plant variables, a trend of positive complementarity and negative selection effects were present. Plant diversity had no clear effect on sediment porewater nutrient concentrations, indicating weak richness effects on resource use.

Influence of Neighboring Plants on Shading Stress Resistance and Recovery of Eelgrass, Zostera marina L

“…At 2–5 m depth grows a seagrass meadow dominated by eelgrass Zostera marina (L.), perfoliate pondweed Potamogeton perfoliatus (L.) and sago pondweed Potamogeton pectinatus (L.), while stands of slender-leaved pondweed Potamogeton filiformis (Pers.) and horned pondweed Zannichellia palustris (L.) grow both within the meadow and as monospecific stands on bare sand [33], [34]. Patchy occurrences of Eurasian water-milfoil Myriophyllum spicatum L. and ditchgrass Ruppia cirrhosa (Petagna) Grande are also found within the meadow.…”

“…During the experiment the temperature ranged between 14°C in June to 20°C in August. The experimental area is semi-exposed with an average water depth of 2.0 m. The nearshore area consists of a sandy, mostly unvegetated area with sediment dominated by fine (∼ 70% 0.125 mm) and very fine (∼5% 0.0062 mm) sand with low (<0.5%) organic content [33]. At 2–5 m depth grows a seagrass meadow dominated by eelgrass Zostera marina (L.), perfoliate pondweed Potamogeton perfoliatus (L.) and sago pondweed Potamogeton pectinatus (L.), while stands of slender-leaved pondweed Potamogeton filiformis (Pers.)…”

“…All experimental plants were collected from nearby plant assemblages and transplanted within six hours. To facilitate in situ planting, plants were gently tied to 30×30 cm plastic grids (mesh size 30 mm, [33]). To investigate rhizome and root growth, Z. marina rhizomes were attached to the grid at the first rhizome internode.…”

“…In the Baltic Sea, eelgrass grows in polycultures (commonly 5–10 angiosperms) with positive effects on ecosystem functioning and eelgrass performance [33], [34] Throughout this region, the water transparency has significantly decreased during the past 30 years, and the occurrence of both cyanobacterial and macroalgal blooms has increased [35]. Consequently, the Baltic angiosperm communities are subjected to increasing chronic light-limitation, but simultaneously grow in naturally diverse meadows where facilitative interactions potentially occur [34].…”

Introduction

“…Next, Christie et al (2009) use data compiled from a number of sources to examine the role of macrophytes as habitat for other fauna and highlight how the presence of some species are important for the persistence of others. The documentation of change in species distributions in existing (Blight et al 2009) and future (Hawkins et al 2009) environments is essential for understanding how climate change affects marine communities, as are experimental manipulations of model communities in the laboratory and field for establishing the importance of biodiversity for ecosystem functioning (Salo et al 2009). These concepts are extended to account for the role of other components of natural systems that influence ecosystem properties: use statistical partitioning to distinguish the relative importance of biodiversity and environmental variables along a gradient of organic enrichment for an important ecosystem process, whilst Josefson (2009) uses similar methodology to examine how diversity and environmental parameters change across spatial scales that extend to the km level.…”