The influence of agricultural land-use on plant and macroinvertebrate communities in springs

Abstract

Many freshwater cool springs can be characterized by nearly constant temperatures and chemical composition. Agricultural activities may leach nutrients to the groundwater, add sediment and nutrients from overland flow, and change the cover of the riparian area surrounding springs, all factors that influence aquatic invertebrate and plant communities. Twenty limnocrene springs in Prince Edward Island, Canada (10 surrounded by and within 20 m of agricultural land, and 10 located in forested areas with < 5% agriculture within 1 km) were studied to determine effects of agricultural activities on invertebrate and plant community structure. Chemical, flow, sediment, and cover variables were examined in all 20 springs, and invertebrates and macrophytes were evaluated in a subset of four agricultural and four forested springs. Although nutrients (particularly nitrate) were higher in agricultural springs than in forested ones, and plant communities differed between springs in the two land use types, light level (relating to the riparian canopy in the two landuse types) was a stronger predictor of aquatic plant community composition than nutrients. Plant diversity was highest in open agricultural sites. Overall invertebrate richness and abundance were higher in forested sites than agricultural sites, but invertebrate community composition differed between the two land-use types, and was primarily related to aquatic plant composition. Few taxa responded directly to elevated nutrients. The composition of the riparian area may be more important than direct inputs of nutrients and sedimentation when assessing agricultural impacts on springs.

Factors Influencing Brook Trout (Salvelinus frontinalis) Egg Survival and Development in Streams Influenced by Agriculture

“…If bacterial biomass is higher in proportion to higher sediment organic content, bacterial decomposition may reduce oxygen in the sediments. Nutrient concentrations in bubbling springs adjacent to agricultural areas are also high in PEI (Knysh et al, 2016). Nutrients from agricultural runoff may have contributed to the establishment of higher organic matter in the incubators in the Wheatley and Souris Rivers through stimulating bacterial production.…”

“…PEI streams are dominated by groundwater and groundwater seeps and PEI springs have a temperature of just over 7ºC throughout the year, reflecting the mean annual temperature of the region (Knysh et al, 2016). Increased survival at warmer stations may have been due to increased oxygen supply from the upwelling water as groundwater on PEI is always oxic (Kynsh et al, 2016).…”

Otolith microchemistry and acoustic telemetry reveal anadromy in non-native rainbow trout (Oncorhynchus mykiss) in Prince Edward Island, Canada

“…PEI, Canada's smallest province (5620 km 2 ) has many short (10-20 km) watersheds fed by groundwater sources (Jiang and Somers 2009;Knysh et al 2016). Pleistocene glacial melt over sedimentary glacial till carved many short drainage basins into the landscape.…”

Inorganic nitrogen has a dominant impact on estuarine eelgrass distribution in the Southern Gulf of St. Lawrence, Canada

“…This is because the nutrient load, which derives largely from fertilizer applied to row crops, is groundwater‐dominated with nutrient surface run‐off being an insignificant contributor to the overall load (Jiang et al ). The shallow aquifers in the region remain saturated in oxygen (Kynsh et al ) and thus the oxidized form of nitrogen entirely predominates. For the three New Brunswick watersheds, the converse is true, there is higher organic matter from natural peat sources consistent with higher total nitrogen.…”