Mapleleaf mussel (Quadrula quadrula) COSEWIC assessment and status report: chapter 5

Habitat

Habitat requirements

Quadrula quadrula is found in a variety of habitats, including medium to large rivers with slow to moderate current, big river embayments, shallow lakes and in deep river impoundments. It has been recorded from mud, sand, and gravel substrates. Preferred substrates have been reported as sand and fine gravel (Parmalee and Bogan 1998) to mud and sand (Clarke 1981). This variability likely reflects the adaptability of this species to particular habitats and a variety of substrates. In Canada Q. quadrula is most typically recovered from medium to large rivers in firmly packed coarse gravel and sand to a substrate of firmly packed clay/mud. Quadrula quadrula is usually recovered at the surface of the substrate in the “tombstone” position with its posterior margins exposed to the water current and the anterior firmly embedded in the substrate. In both Manitoba and Ontario it has been recorded historically from larger lakes, but recent data indicate it has largely been lost from these habitats (Pip, pers. comm.; Schloesser and Nalepa, 1994).

Habitat trends in Ontario

The invasion of the Great Lakes by the zebra mussel began in 1986 and resulted in the near extirpation of native mussels from Lake Erie, Lake St. Clair and the Detroit and Niagara Rivers by the mid-1990s. Only isolated communities with reduced species richness and low abundance still survive in several bays and marshes along the U.S. shore of Lake Erie and in the delta area of Lake St. Clair. As Quadrula quadrula has always been rare in these waters, the loss of habitat is less significant for this species than for many other unionids.

Mussel communities in the Grand River declined dramatically from a historical total of 31 species to only 17 by the early 1970s. Kidd (1973) blamed this decline on pollution, siltation and the presence of dams. He found few mussels living below dams or in reservoirs and noted that none of the dams had fishways. He also found that dissolved oxygen concentrations were low and turbidity was high in the lower reaches of the river, most likely due to agricultural runoff. Sewage pollution was probably the major cause of the decline of mussels in this river. At the time of Kidd’s surveys, only 7 of the river’s 22 sewage treatment plants (STPs) had had secondary treatment for 10 years, 7 others had upgraded from no treatment to secondary treatment during that time and the remaining 8 were in the process of installing treatment facilities for the first time. Twenty-five years later, Metcalfe-Smith et al. (2000a) found that the mussel communities of the river had rebounded – most likely in response to significant improvements in water quality. Unfortunately, this trend is unlikely to continue. The population of the watershed doubled from 375,000 to 787,000 between 1971 and 1996 and is expected to grow by another 300,000 over the next 25 years (GRCA 1997). The percentage of the minimum daily flow consisting of treated effluent from STPs ranged from 1% to 22% in 1993 and the capacity of the river to receive additional wastewater at reasonable cost is in question. The proportion of the Grand River basin in agricultural use increased from 68% in 1976 to 75% by 1998 (GRCA 1998). Row crop farming has increased, and along with it the potential for greater soil erosion and runoff of pesticides and fertilizers. Livestock production has changed, becoming more concentrated and specialized, and focusing on pigs and sheep rather than cattle. There has also been a change in manure handling from solid to liquid, and inadequate management of these liquid wastes has become a problem in some areas (GRCA 1998). Cumulative impacts of these stresses will be greatest in the lower reaches of the river where Quadrula quadrula occurs.

Habitat trends in the Sydenham River are summarized from Staton et al. (2003). Prior to European settlement, the Sydenham River watershed was 70% forest and 30% swamp. By 1983, 81% of the land area was in intensive agriculture (mainly corn and soybean crops), with only 12% forest and <1% swamp. Sixty percent of the watershed is tile drained. Total phosphorus (TP) levels have consistently exceeded the provincial water quality objective (PWQO) over the past 30 years. Concentrations of TP and total Kjeldahl nitrogen continue to increase in the species-rich east branch and most of the P is associated with particulate material that probably originates from agricultural runoff. Chloride levels have been relatively low but are slowly increasing – a widespread pattern that is attributed to the increased use of road salt. Sediment loadings from overland runoff and tile drains are high and the north branch of the river is particularly turbid. Wooded riparian zones, which are important for bank stabilization and interception of nutrients and sediments from overland runoff, are very limited. The population of the Sydenham River watershed is small (74,000), with 50% rural and 50% living in towns and villages. Despite a modest rate of population growth, all municipalities have upgraded their sewage treatment facilities over the past 30 years. Leakage of nutrients and contaminants from rural septic systems is a significant and on-going problem, especially in the north branch.

Agriculture is the dominant form of land use in the Thames River watershed, with 78% of the land area in the upper Thames and 88% in the lower Thames in agricultural use (Taylor et al. 2004). Forested areas have been reduced to 12% of the land area in the upper Thames and 5% in the lower Thames. Eight percent of the watershed is classified as urban, with concentrations in the cities of London (population 350,000), Stratford and Woodstock in the upper watershed and Chatham in the lower watershed. As the land was cleared, flooding became a serious problem. Three large dams and reservoirs were constructed in the upper watershed between 1952 and 1965. Numerous private dams and weirs have been installed since the 1980s and there are now 173 structures in the upper and 65 in the lower watershed. The extent of tile drainage is not known. Water quality data collected since the 1960s show that concentrations of phosphorus and heavy metals are declining while nitrate and chloride levels are on the rise. The upper Thames is moderately turbid while the lower Thames, where Quadrula quadrula mainly occurs, is highly turbid. Soil conservation remains a serious issue in the watershed.

Mussel habitat in the Ausable River has been dramatically altered over time. Prior to European settlement, 80% of the basin was covered in forest, 19% was in lowland vegetation and 1% was marsh. By 1983, 85% of the land area was in agriculture (70% in row crops), and only 13% remained in small unconnected woodlots (Nelson et al. 2003). Over 70% of the basin is now in tile drainage. The natural course of the lower portion of the river was destroyed in the late 1800s, when it was diverted in two places to alleviate flooding. The Ausable River has been described as “event responsive”, meaning there are large increases in flow during runoff events following storms. The nearby Sydenham, Thames and Maitland Rivers are more stable in this regard. There are 21 dams in the system causing sediment retention upstream and scouring downstream. Water quality data collected since 1965 show that TP levels are consistently above the PWQO and have decreased only marginally over the past 35 years. Nitrate levels currently exceed federal guidelines for the prevention of eutrophication and the protection of aquatic life and are slowly rising. Mean total suspended solid concentrations in the lower Ausable River, which supports a small population of Quadrula quadrula, exceed levels required for good fisheries.

Habitat trends in Manitoba

The Red River and Assiniboine River drainages flow through what once was tall-grass to mixed-grass prairie. This is one of the most altered biomes on the planet with less than 1% remaining (Meffe and Carroll 1997). European colonization, breaking of the land with the plow and contemporary industrial-scale agriculture have all contributed to the demise of this biome. The majority of the land within these watersheds is now agricultural, being tilled for grain and oilseed crops, being used for grazing, or urban/industrial. A recent development is the growing hog industry with high density hog barns being established throughout the watershed. The effect on the rivers that flow through this landscape cannot be under-estimated. The major current concern is non-point source nutrient enrichment from agricultural runoff (Manitoba Conservation 2000). A second issue is damage to river banks resulting from uncontrolled access of cattle herds to the river. Industrial water removal and usage is also a concern with regard to water quality. The most recent issue relating to water quality in Manitoba relates to industrial hog barns. These are operations raising hundreds to thousands of hogs per site annually. The waste produced is of particular concern either due to the potential for catastrophic spills from storage tanks or from runoff after the waste has been applied to the land as a “natural fertilizer”.

The major concern with respect to habitat in Manitoba is water quality. Jones and Armstrong (2001) analysed existing data on water quality in Manitoba and reported a significant increase in total nitrogen (TN) and total phosphorus (TP) in the Red River and Assiniboine drainage in the past 30 years. These increases ranged from 29% to 62% for phosphorus in the Red and Assiniboine rivers, respectively, and from 54% to 57% for total nitrogen in the Red and Assiniboine rivers, respectively. These two nutrients are major contributors to nutrient enrichment and loading of waterways that can result in cultural eutrophication and degradation of water quality. This study (Jones and Armstrong 2001) was followed up by Bourne et al. (2002) who focused on the Red and Assiniboine watersheds. The data were reported as total nitrogen and phosphorus expressed as tonnes per year due to extreme variation in nutrient loads at weekly, seasonal and yearly time scales. They (Bourne et al. 2002) found that nutrient enrichment was substantial and primarily resulted from non-point sources, in particular agricultural runoff. Bourne et al. (2002) reported that from 1994-2001 the Assiniboine River on average carried 3,682 tonnes per year of total nitrogen and 637 tonnes per year of total phosphorus near its outflow into the Red River. During this same time period, the Red River on average carried 15,301 tonnes per year total nitrogen and 4,269 tonnes per year total phosphorus. The result of this nutrient input has been the increasing eutrophication of Lake Winnipeg such that basin-wide algae blooms are visible from space (http://www.cbc.ca/manitoba/features/lakewinnipeg/special.html).

There is an accumulating body of evidence that freshwater mussels are sensitive to ammonia at levels below what is acceptable by the U.S. Environmental Protection Agency (Augspurger et al. 2003, Bartsch et al. 2003, Mummert et al. 2003). The juvenile stage appears most vulnerable to this exposure, which can result in adult populations persisting, but no recruitment. This could lead to the illusion of a healthy population based on the persistence of adult populations. None of the aforementioned studies specifically tested Quadrula quadrula, or any members of that genus. However, tests revealed juvenile sensitivity to low ammonia concentrations across a variety of species (Augspurger et al. 2003) that may be extended to Q. quadrula. The increasing trajectory of N loading in Manitoba streams coupled with the apparent absence of recruitment into the existing Q. quadrula populations is therefore of concern. 

Habitat protection/ownership

Ontario

Land ownership along the reaches of the Sydenham, Thames, Ausable and Grand Rivers where Quadrula quadrula occurs is mainly private and in agricultural use. Only two small properties in the Sydenham River watershed, the 7 ha Shetland Conservation Area and the 20 ha Mosa Township forest, are publicly owned and somewhat protected (M. Andreae, pers. comm. 1998). There are 21 natural areas totalling 6,200 ha in the Thames River watershed, but only one – the 16 ha Big Bend Conservation Area – is located in the same reach as Q. quadrula (Thames River Background Study Research Team 1998). Also in this reach are four Indian Reserves (Delaware of Moraviantown, Munsee Delaware, Oneida of the Thames and Chippewa of the Thames) that occupy over 6,700 ha of land along ~ 45 km of the river. The Ausable Bayfield Conservation Authority owns a number of properties totalling 1,830 ha throughout the basin (Snell and Cecile Environmental Research 1995). Less than 3% of the land in the Grand River watershed is publicly owned (GRCA 1998). There are 11 conservation areas, only one of which (Byng Island) is located within Q. quadrula’s range in the river. It should be noted that recovery strategies and action plans are being developed/implemented for the Sydenham, Thames and Ausable River aquatic ecosystems to protect and recover aquatic and semi-aquatic species at risk including fishes, mussels, turtles and snakes. Many landowners are participating in riparian rehabilitation projects and improved land use practices that will ultimately benefit all aquatic species.

Manitoba

Land ownership on the Assiniboine, Red and Roseau Rivers was determined using GIS from 1:500,000 base maps for the water layer. Land along these rivers is predominately privately owned and in agricultural use. Approximately 19% of the Red River could be considered urban, passing through Winnipeg and Selkirk. With the exception of small towns, the remainder is agricultural. There are no protected lands along the Red River. The Roseau River flows through no protected lands or designated areas. Approximately 7% is Crown land, 9% is Indian Reserve land and the remaining 84% is patented land used mostly for agriculture. If we consider the entire length of the Assiniboine River within Manitoba (approximately 1,000 km) then 84% of the surrounding land is privately held and agricultural, 6% is urban and approximately 10% flows through either a park or a Wildlife Management Area (WMA). Approximately 60% of these parks or WMAs are designated as protected, meaning mining, logging, hydro-electric development and other activities that affect wildlife habitat are prohibited. The non-protected parks and WMAs are designated Crown lands without a regulation or order in council specifying that land is to be protected. It should be noted that about half of these designated lands, whether protected or not, lie on one bank of the river, with the opposite bank being privately held. However, if we consider just the stretch of the Assiniboine downstream from the Portage Diversion to the confluence with the Red River, there is only 7% flowing through protected land (Beaudry Provincial Park). The remainder is 80% agricultural and 13% is urban, flowing through Winnipeg.

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