TY - JOUR

T1 - Influence of quantity and lability of sediment organic matter on the biomass of two isoetids, Littorella uniflora and Echinodorus repens

AU - Pulido Pérez, Cristina

AU - Lucassen, E.C.H.E.

AU - Pedersen, Ole

AU - Roelofs, J.G.M.

PY - 2011

Y1 - 2011

N2 - P>1. Despite real improvement in the water quality of many previously eutrophic lakes, the recovery of submerged vegetation has been poor. This lack of recovery is possibly caused by the accumulation of organic matter on the top layer of the sediment, which is produced under eutrophic conditions. Hence, our objective was to study the combined effects of quantity and lability of sediment organic matter on the biomass of Echinodorus repens and Littorella uniflora and on the force required to uproot plants of L. uniflora. 2. Lake sediments, rich in organic matter, were collected from four lakes, two with healthy populations of isoetids and two from which isoetids had disappeared. The four lake sediments were mixed with sand to prepare a range of experimental sediments that differed in quantity and lability of sediment organic matter. Two isoetid species, E. repens and L. uniflora, were grown in these sediments for 8 weeks. Sediment quality parameters, including elemental composition, nutrient availability and mineralisation rates, were determined on the raw sources of sediment from the lakes. Porewater and surface water were analysed for the chemical composition in all mixtures. At the end of the experiment, plants were harvested and their biomass, tissue nutrient concentration and (for L. uniflora) uprooting force were measured. 3. For both species, all plants survived and showed no signs of stress on all types of sediment. The biomass of E. repens increased as the fraction of organic matter was increased (from 6 to 39% of organic content, depending upon sediment type). However, in some of the sediment types, a higher fraction of organic matter led to a decline in biomass. The biomass of L. uniflora was less responsive to organic content and was decreased significantly only when the least labile sediment source was used to create the gradient of organic matter. The increase in shoot biomass for both species was closely related to higher CO(2) concentrations in the porewater of the sediment. The force required to uproot L. uniflora plants over a range of sediment organic matter fitted a Gaussian model; it reached a maximum at around 15% organic matter and declined significantly above that. 4. Increasing organic matter content of the sediment increased the biomass of isoetid plants, as the positive effects of higher CO(2) production outweighed the negative effects of low oxygen concentration in more (labile) organic sediments. However, sediment organic matter can adversely affect isoetid survival by promoting the uprooting of plants

AB - P>1. Despite real improvement in the water quality of many previously eutrophic lakes, the recovery of submerged vegetation has been poor. This lack of recovery is possibly caused by the accumulation of organic matter on the top layer of the sediment, which is produced under eutrophic conditions. Hence, our objective was to study the combined effects of quantity and lability of sediment organic matter on the biomass of Echinodorus repens and Littorella uniflora and on the force required to uproot plants of L. uniflora. 2. Lake sediments, rich in organic matter, were collected from four lakes, two with healthy populations of isoetids and two from which isoetids had disappeared. The four lake sediments were mixed with sand to prepare a range of experimental sediments that differed in quantity and lability of sediment organic matter. Two isoetid species, E. repens and L. uniflora, were grown in these sediments for 8 weeks. Sediment quality parameters, including elemental composition, nutrient availability and mineralisation rates, were determined on the raw sources of sediment from the lakes. Porewater and surface water were analysed for the chemical composition in all mixtures. At the end of the experiment, plants were harvested and their biomass, tissue nutrient concentration and (for L. uniflora) uprooting force were measured. 3. For both species, all plants survived and showed no signs of stress on all types of sediment. The biomass of E. repens increased as the fraction of organic matter was increased (from 6 to 39% of organic content, depending upon sediment type). However, in some of the sediment types, a higher fraction of organic matter led to a decline in biomass. The biomass of L. uniflora was less responsive to organic content and was decreased significantly only when the least labile sediment source was used to create the gradient of organic matter. The increase in shoot biomass for both species was closely related to higher CO(2) concentrations in the porewater of the sediment. The force required to uproot L. uniflora plants over a range of sediment organic matter fitted a Gaussian model; it reached a maximum at around 15% organic matter and declined significantly above that. 4. Increasing organic matter content of the sediment increased the biomass of isoetid plants, as the positive effects of higher CO(2) production outweighed the negative effects of low oxygen concentration in more (labile) organic sediments. However, sediment organic matter can adversely affect isoetid survival by promoting the uprooting of plants

KW - CH(4) production

KW - CO(2) production

KW - sediment mineralisation

KW - softwater lakes

KW - uprooting

KW - AQUATIC CARBON-DIOXIDE

KW - DANISH LOBELIA-LAKE

KW - MACROPHYTE COMMUNITIES

KW - SOFT WATERS

KW - GRANE-LANGSO

KW - L ASCHERS

KW - CO2

KW - EUTROPHICATION

KW - GROWTH

U2 - 10.1111/j.1365-2427.2010.02539.x

DO - 10.1111/j.1365-2427.2010.02539.x

M3 - Journal article

VL - 56

SP - 939

EP - 951

JO - Freshwater Biology

JF - Freshwater Biology

SN - 0046-5070

IS - 5

ER -