Deleterious interaction of light impairment and organic matter enrichment on Isoetes lacustris (Lycopodiophyta, Isoetales)

Abstract

Light reduction and increased organic matter load often occur together in lakes undergoing eutrophication. We aimed at experimentally testing the relative importance of light availability, organic matter enrichment and their interactions in the collapse of healthy populations of Isoetes lacustris. We conducted an in situ shading (65 and 35% of incident light) and organic matter enrichment (10% enrichment) experiment in a Pyrenean pond (NE Spain). We followed plant performance using growth indicators, carbon balance indicators and individual survival. Severe light reduction (35%) resulted in a lengthening of the new leaves and no effects on mortality. Organic matter enrichment resulted in lower production and increased individual mortality. The combination of both stresses resulted in stronger negative effects and the highest mortality rate, which helps explaining I. lacustris die-offs observed after damming. Under severe light reduction (35%), plants used corm starch to keep growing. Consequently, starch percentage decreased and sucrose percentage increased as it was transported to the growing leaves. The most extreme changes were observed under severe light reduction and fertilization, which extremely increased the ratio between sucrose and total non-structural carbohydrates (TNC). Thus, I. lacustris sucrose:TNC ratio is a good indicator of light reduction and organic matter enrichment stresses.

Biogeochemical Responses to Holocene Catchment‐Lake Dynamics in the Tasmanian World Heritage Area, Australia

“…6 ka (Figure b). While comparatively little is known about the ecology of Tasmanian Isoëtes species (Garrett & Kantivalis, ), evidence indicates an increase in mortality in response to a reduction in the penetration of light through the water column in the widespread European and North American species, Isoëtes lacustris (Chappuis et al, ; Riera et al, ). Thus, in combination with the evidence for changes in dystrophy in Dove Lake, we interpret the low relative values of Isoëtes prior to ca.…”

“…The ratio between rainforest and sclerophyll plant taxa (rainforest:sclerophyll) was calculated from the land‐cover data published in Mariani et al () prior to the elaboration of statistics (see below). From the same data set, Isoëtes , a littoral macrophyte, spore abundances were considered as proxy for aquatic conditions, such as lake level and light penetration variation (Bogotá‐A et al, ; Chappuis et al, ; Finkenbinder et al, ; Pesce & Moreno, ; Simi et al, ).…”

Non-native Minnows Threaten Quillwort Populations in High Mountain Shallow Lakes

“…Total macrophyte biomass per unit area was marginally affected by the presence of non-native fishes but the biomass allocation within the shoot varied substantially among scenarios. Quillworts show very high plasticity of the photosynthetic tissues (Hickey, 1986 ; Chappuis et al, 2015 ) with increasing above against belowground biomass under conditions of low light availability. In minnow lakes, high water column light attenuation levels and high epiphytic biomass were coupled to an increase of up to 6 times the biomass of quillwort leaves at expenses of the belowground compartments (shoots and roots) and reproductive effort (sporangia).…”

“…The carbohydrate concentration in the different carbon storage plant compartments (i.e., leaves, sporangia at the base of the leaves, and corms) was determined by pooling together ten individuals from each lake collected at −2 m depth. Although leaves from different ages (i.e., different position in the rosette) show some variation in total carbohydrate content (Chappuis et al, 2015 ), all the leaves were pooled together based on the fact that plants were collected at the end of the growing period in October, and thus we measured average carbon storage for the population before winter. Plant compartments were sorted, dried and grinded for further analysis following the method described in Alcoverro et al ( 2001 ) and the extracts read in a spectrophotometer Shimadzu uv-2401 PC.…”

Assessing the conservation status of Mediterranean temporary ponds using biodiversity: a new tool for practitioners

“…In our set of indicators, plants were the most represented biological group, probably because they are extremely sensitive to habitat disturbances (Rhazi et al, 2001(Rhazi et al, , 2006Crosslé & Brock, 2002;Bagella et al, 2010;Bouahim et al, 2010). Plant composition in wetlands is influenced mainly by hydrologic regime (Casanova & Brock, 2000;Della Bella et al, 2008) and water quality (Lumbreras et al, 2013;Rosset et al, 2014;Chappuis et al, 2015). The disturbance of these two factors by drainage, excavation, irrigation or eutrophication may have severe impacts on plant species in wetlands and specifically in Mediterranean temporary ponds (Rhazi et al, 2001;Serrano & Zunzunegui, 2008;Lumbreras et al, 2012;Rosset et al, 2014).…”