07_06042_aquaticplants.qxd:CFN 121(2) 10/17/08 1:50 PM Page 164 An Inventory of the Aquatic and Subaquatic Plants in SASKWater Canals in Central Saskatchewan, Canada, Before and After the Application of the Herbicide Magnacide J. HUGO COTA-SÁNCHEZ1 and KIRSTEN REMARCHUK Department of Biology and Herbarium of the University of Saskatchewan, University of Saskatchewan, 112 Science Place, Saskatoon, Saskatchewan S7N 5E2 Canada 1 Corresponding author: [email protected] Cota-Sánchez, J. Hugo, and Kirsten Remarchuk. 2007. An inventory of the aquatic and subaquatic plants in SASKWater canals in central Saskatchewan, Canada, before and after the application of the herbicide Magnacide. Canadian Field-Naturalist 121(2): 164–167. This study focuses on the floristic composition of aquatic and semi-aquatic plants in the SASKWater canal system and their potential effect on irrigation systems. A checklist, evaluation, and synthesis of the species identified in this survey before and after the application of the herbicide Magnacide are provided, in addition to a brief discussion of the environmental effects of Magnacide. Thirty-three species in 26 genera within 20 plant families were identified. Two unidentified green algae were also collected. Common aquatics (i.e., green algae, Potamogeton spp., Alisma gramineum, A. plantago-aquatica, Ceratophyllum demersum, and Myriophyllum sibiricum) combined with debris from terrestrial plants were the primary contributors to block- age of irrigation drains. In general, the concentration of Magnacide used in this study had a minor effect on aquatic plant diversity, but effectively reduced plant density. However, the long-term effects of pesticides on the surrounding aquatic and terrestrial environments of the SASKWater irrigation system are unknown. Key Words: aquatic plant inventory, environmental effect, SASKWater canals, Magnacide, acrolein, Saskatchewan. Plants are vital to the function of aquatic ecosystems aquatic plant debris from entering the system. for their role in providing food, oxygen, and habitat for Aquatic species impede water flow by clogging other organisms. However, floating and submerged gates, intake screens, valves, and pumps in irrigation vegetation along with debris from terrestrial plants and drainage channels (Lancar and Krake 2002). As a may be problematic in different types of water bodies. consequence, localized flooding may result under high For example, in shallow lakes, profuse plant growth water conditions. In addition, Holm et al. (1969) indi- creates dense mats that prevent the regular movement cate that abundant vegetation in canals can lead to an of watercraft. In addition, aquatic plants, including excessive loss of water through evapotranspiration. algae, can significantly reduce the aesthetic value of pondweed (Potamogeton L.), Milfoil (Myriophyllum water bodies. Furthermore, rapid growth of vegetation sibiricum), Canada Waterweed (Elodea canadensis), and deposition of debris in irrigation canals can result wild celery (Vallisneria L.), and American Eel-grass in a decline in water flow rates and a subsequent in - (Zostera marina L.) are a few of the problematic coarse ability to supply water to crops. Hence, the removal of or large species in shallow aquatic environments (Lan- selected aquatic species via physical or chemical meth- car and Krake 2002). ods may be required to improve ecosystem function, Of particular interest to this study are aquatic taxa aesthetic value, and availability for human consump- that interfere with canal irrigation systems in central tion. Saskatchewan. Accelerated growth of plants in SASK - Aquatic plants can be placed into four broad cate- Water canals restricts the amount of water available for gories: (1) algae, (2) floating-leaved, (3) submerged, and irrigation. Given the clogging effect of aquatic plant (4) emergent plants (Shelton and Murphy 1989). Of the growth on water flow, agricultural canals were treated four categories listed above, algae are of the greatest with Magnacide, a volatile algaecide and aquatic her- concern in canal systems because of the likelihood of bicide, in which the active ingredient is acrolein (Score- interfering with water flow. Algae grow profusely in card 2006*). Acrolein contains two functional groups, slow moving, shallow water. Floating-leaved and sub- a reactive double bond and an aldehyde group (Nor- merged plants are rooted, with the foliage at or below done et al. 1996) and is, in turn, toxic to some organ- the water surface. Flowing water or disturbance, such isms (Albariño et al. 2007). However, it is widely used as wind, can uproot plants leading to subsequent ob - in agricultural canals and water bodies as an herbicide struc tion of water flow. Finally, emergent species typ- to control aquatic weeds (Burland et al. 1984; San- ically grow in shallow, fluctuating water, such as drain - godoyin and Smith 1996). The use of high concentra- age ditches, canals, rivers, periphery of water bodies, tions of acrolein could pose a significant risk to aquat- and ponds. Plants in this category are of minor concern ic environments (Nordone et al. 1996); therefore, the in canal systems and in some cases may prevent non- controlled application and use of Magnacide and other 164 07_06042_aquaticplants.qxd:CFN 121(2) 10/17/08 1:50 PM Page 165 2007 COTA-SÁNCHEZ and REMARCHUK: AQUATIC AND SUBAQUATIC PLANTS 165 herbicides is highly recommended. Previous studies species were eradicated from the sites as a result of have shown that toxic residues deposited in soils and Magnacide application; that is, the same species were water bodies have detrimental effects in the life cycles identified before and after the treatment. However, of local flora and fauna (Sangodoyin and Smith 1996). the plant density was noticeably lower after the treat- Thus, even though several sources, e.g., Sangodoyin ment with Magnacide. Various submerged species in - and Smith (1996); Nordone et al. (1996); Albariño et cluding Potamogeton richardsonii, P. pectinatus, and al. (2007), claim that the transient use of acrolein in the unknown green algae were present in most of the agricultural waters at minimal amounts has no negative sites surveyed. Other aquatics, e.g., Elodea canadensis impact in natural aquatic environments, rigid control and Lemna trisulca, were less frequent and account- must be enforced to prevent ecological damage. ed for a smaller proportion of plant biomass in the In this study, we investigated the floristic composi- canal system. Emergent species in the Cyperaceae, tion of aquatic and semi-aquatic plants in the SASK - Equisetaceae, and Asteraceae do not appear to play a Water canal system and their potential effect on ir - role in impeding water flow, but floating debris from rigation systems. Our study is a contribution to the non-aquatic taxa, such as Melilotus albus and Hordeum know ledge of Saskatchewan aquatic and sub-aquatic jubatum, contributes to the clogging of intake screens flora and provides a preliminary assessment and syn- throughout the canal system. thesis of the species identified prior to and after the Based on this survey, it is not possible to determine application of Magnacide. The potential effect of a single species that adversely affects water flow by Mag nacide on aquatic flora is also discussed. clogging intake screens in the SASKWater canal sys- tems. A combination of common aquatic plants (Pota- Methods mogeton spp., Alisma gramineum, A. plantago-aquat- Compared to most wetland inventories, this survey ica, Ceratophyllum demersum, and Myriophyllum covers a limited geographic area and a restricted range sibiricum), which are frequently dislodged by flowing of wetland flora. The site selection and sampling strat- water or wind, are the primary contributors to blockage egy were designed to survey all major areas of the of drains and intake screens. The presence of large, SASK Water canal system to be evaluated in terms of coarse water pondweeds such as Potamogeton spp. and aquatic vegetation within the Saskatoon Southeast Water other filamentous species in SASKWater canals is un - Supply Project Location Plan (Brightwater-Blackstrap- desirable because their accumulation affects the reg- Zelma Reservoir areas; 51°25' to 52°55'N, 106°15' to ular water flow. A similar situation has been reported 107°00'W). This system irrigates an estimated area of in the Alberta irrigation systems (Burland and Catling 20 120 acres. The survey sites include locations of 1986). In addition, green algae are common and are Magnacide application by SASKWater personnel at presumably the greatest problem in clogging the in - intake screens. Acrolein was directly applied to water take screen systems because of their filamentous nature in strategic sites to control submersed, floating and and massive growth. Furthermore, some plants or frag- emergent aquatic weeds. The herbicide was applied at ments from non-aquatic plants, particularly Melilotus a concentration of 2.5-5.0 ppm/30 minutes every two albus and Hordeum jubatum, are involved in reducing weeks from June through August 2005 in an attempt to water flow because the species tend to concentrate near eradicate aquatic species with excessive growth rates the uptake areas, especially in the vicinities of mowed (J. Mander, SASKWater, personal communication). ditches along the canals. Surveys were conducted before and after the chemi- Since this survey is mainly concerned with the flo - cal treatment to determine the effect of Magnacide r istic composition of the SASKWater canal system and