Assessing the ecological impact of banana farms on water quality using aquatic macroinvertebrate community composition

In Costa Rica considerable effort goes to conservation and protection of biodiversity, while at the same time 30 agricultural pesticide use is among the highest in the world. Several protected areas, some being wetlands or 31 marine reserves, are situated downstream large-scale banana farms, with an average of 57 pesticide applications 32 per year. The banana industry is increasingly aware of the need to reduce their negative environmental impact, 33 but few ecological field studies have been made to evaluate the efficiency of proposed mitigation strategies. This 34 study compared the composition of benthic macroinvertebrate communities up- and downstream effluent water 35 from banana farms in order to assess whether benthic invertebrate community structure can be used to detect 36 environmental impact of banana farming, and thereby usable to assess improvements in management practices. 37 Aquatic invertebrate samples were collected at 13 sites, using kick-net sampling, both up- and downstream 38 banana farms in fast flowing streams in the Caribbean zone of Costa Rica. In total, 2888 invertebrate specimens 39 were collected, belonging to 15 orders and 48 families or taxa. The change in community composition was 40 analyzed using multivariate statistics. Additionally, a biodiversity index and the Biological Monitoring Working 41 Party (BMWP) score system was applied along with a number of community composition descriptors. 42 Multivariate analyses indicated that surface waters immediately up- and downstream large-scale banana farms 43 have different macroinvertebrate community compositions with the most evident differences being higher 44 dominance by single taxa and a much higher total abundance, mostly of that same taxon. Assessment of 45 macroinvertebrate community composition thus appears to be a viable approach to detect negative impact from 46 chemical-intensive agriculture and could become an effective means to monitor the efficacy of changes/proposed 47 improvements in farming practices in Costa Rica and similar systems.