The impact of conifer plantation forestry on the Chydoridae communities of blanket bog lakes Tom J. Drinan, Conor T. Graham, John O’Halloran and Simon S.C. Harrison HYDROFOR Project

Background Plantation forests cover an estimated 10% of the Irish land surface area. Many of these plantations are on peat soils Extensive afforestation of peat soils has taken place since the 1950’s – this crop is now reaching harvestable age Previous studies have demonstrated a high risk of plant nutrient and sediment run-off to receiving waters from afforested catchments, particularly on peat soils There is a clear risk to the ecological status of high conservation value peatland water bodies from catchment forestry operations

To investigate how conifer plantation forestry operations affect blanket bog lakes in terms of: 1) Their hydrochemical status 2) Their Chydoridae (Cladocera) communities Aims

Study design Igneous (Granite) Geology 7 lakes non-forested (‘blanket bog’) 7 lakes afforested: 4 lakes surrounded by mature conifer forests (‘mature plantation’) 3 lakes surrounded by clearfelling (‘clearfell’) Sedimentary (Sandstone) Geology 6 lakes non-forested (‘blanket bog’) 6 lakes afforested: 3 lakes surrounded by mature conifer forests (‘mature plantation’) 3 lakes surrounded by clearfelling (‘clearfell’)

Study lakes GB1 GB2 GM1 GM2 GB3 GB4 GM3 GM4 GB5GC1 GB6GC2 GB7GC3 SB3 SB4 SB5 SB6 SC1 SC2 SC3 SB1 SB2 SM1 SM2 SM3 The lakes underlain by granite are located at lower altitude and in closer proximity to the coast than the lakes underlain by sandstone S = Sandstone G = Granite B = Blanket bog M = Mature plantation C = Clearfell

Blanket bog lake: catchment containing only undisturbed blanket bog

Mature plantation lake: catchment dominated by closed- canopy conifer plantation

Clearfell lake: catchment containing mature conifer plantation with recently (within 2 – 5 years) clearfelled areas

Water Chemistry Dip samples (a single sample from the water column) were taken every two months from each lake, beginning March 2009 We measured pH, conductivity, temperature, dissolved oxygen, colour, alkalinity, TDOC, TP, SRP, TN, TON, ammonia, SO 4, Ca, Na, Cl, Mg, Al, Mn and Fe Chydoridae Semi-quantitative method: slowly sweeping a hand-held sweep net (100 μm mesh, 0.15 m diameter frame) horizontally both inside and outside a stand of vegetation for 30 seconds in the littoral zone of each lake Methodology

Results – water chemistry b) Water Chemistry PCA Higher plant nutrients, TDOC, major ions, heavy metals, and reduced dissolved oxygen concentrations in lakes with forestry a)  Sandstone blanket bog  Granite blanket bog Sandstone mature plantation  Granite mature plantation Sandstone clearfell  Granite clearfell

Ammonia Soluble Reactive Phosphorus Sandstone Granite Total Nitrogen Results – water chemistry Chlorophyll a

Dissolved oxygen Dissolved organic carbonpH Total monomeric aluminium Sandstone Granite Results – water chemistry

Likely sources of forestry inputs include: Decomposition of the clearfell residue (brash, foliage etc.) Decomposition of peat soil Artificial fertilisers applied during the forest crop cycle Potential impacts of forestry-mediated hydrochemical change: Enhanced autotrophic and heterotrophic production Reduced dissolved oxygen concentrations Elevated heavy metal concentrations. Discussion of water chemistry

Chydorid community nMDS  Sandstone blanket bog  Granite blanket bog Sandstone mature plantation  Granite mature plantation Sandstone clearfell  Granite clearfell Results – chydorids

Sandstone Granite Alonopsis elongata Chydorus sphaericus Alonella nana Alonella excisa Results – chydorids

Alonopsis elongata dominant in blanket bog lakes and Chydorus sphaericus, Alonella nana and Alonella excisa dominant in clearfell and mature plantation lakes Only two individuals of a single species (Alona guttata) were recorded from a recently clearfelled lake underlain by granite. This lake also contained the highest concentrations of Al & Fe Alonella excisa was more abundant in sandsone lakes Results – chydorids

Discussion of chydorids Increased autotrophy and heterotrophy leads to a reduction in size of the dominant food particles available A. elongata feeds on larger food particles, C. sphaericus, A. nana and A. excisa feed on smaller food particles C. sphaericus is more tolerant to the general decline in lake water quality Toxicity from heavy metals only important following recent extensive catchment clearfelling The higher pH and base cation concentration, driven primarily by marine sea-spray deposition, may account for geological effects on chydorids

Chydorid community change is consistent with conifer plantation forestry exerting a trophic, rather than an acidic or toxic effect on lake ecosystems Conclusions Plantation forestry effect was consistent across geologies and regions, indicating that the anthropogenic effect overrides any effect of catchment geology, altitude and proximity to sea

This study was funded by the HYDROFOR project which is co-funded by the Department of Agriculture, Fisheries and Food, and Environmental Protection Agency (EPA) under the STRIVE Programme 2007–2013 We thank Dr. Elvira de Eyto for her help with zooplankton identification and various aspects of the research Acknowledgements