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Great Blue Heron: a Sentinel Species for the State of the St. Lawrence

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Great Blue Heron: a Sentinel Species for the State of the St. Lawrence BIOLOGICAL RESOURCES WATER SEDIMENTS SHORELINES USES 3rd edition Great Blue Heron: A Sentinel Species for the State of the St. Lawrence The Great Blue Heron was selected as a sentinel Indicator: Contamination species, or bioindicator, of the state of the St. of the Great Blue Heron Lawrence because it occurs in both marine by toxic substances and freshwater environments, occupies a State: moderate-good position at the top of the food chain, and has a relatively limited foraging range. Contaminant concentrations in Great Blue Heron eggs indicate local contamination of the ecosystem Background they are breeding in. At high concentrations, a number of contaminants are extremely toxic There are many different factors that can impact and can cause mortality. At the concentrations bird populations, from climatic conditions to typically observed in the environment, these human disturbance. Despite conservation and contaminants are less protection efforts, toxic substances transported toxic but can have adverse through water and air from large urban and effects on essential industrial centres and from agricultural areas biological functions, such can accumulate in the environment and have as growth, reproduction harmful effects on wildlife. A large number of and ability to fight chemicals, including organochlorine pesticides infection. For instance, (such as DDT), polychlorinated biphenyls (PCBs) some chemicals closely and polybrominated diphenyl ethers (PBDEs), resemble hormones and break down very slowly and tend to accumulate can interfere with the in increasingly higher concentrations at each transmission of chemical successive level of the food chain. For that messages responsible for Great Blue Heron Photo: Christian Marcotte reason, fish-eating birds are often used as proper functioning of the © Environment and Climate bioindicators of ecosystem health. organism. Change Canada BIOLOGICAL RESOURCES WATER SEDIMENTS SHORELINES USES Overview of the situation contains close to 700 nests. The total Quebec population of Great Blue Herons is estimated A migratory species sensitive to disturbance, the at approximately 27 000 individuals, one third Great Blue Heron nests in colonies, or heronries, of which nest along the St. Lawrence. These in treetops, typically on islands in lakes or in results must be interpreted with caution, beaver ponds that are relatively inaccessible however, since the survey covers only known to humans and terrestrial predators. These heronries, rather than all heronries. colonies can be found in every region of Quebec, including some 30 along the St. Lawrence, from In the 2012 survey of Great Blue Heron colonies, Lake Saint-François, upstream, to Sept-Îles and the average number of young per clutch was the Magdalen Islands in the Gulf (Figure 1). 2.95 in the St. Lawrence (Figure 2), compared Colonies vary in size from year to year but with 2.35 in Quebec as a whole, while typically number roughly several dozen pairs. average productivity (number of fledglings After a period ranging from several years to relative to the number of eggs laid, expressed several decades, depending on the size of the as a percentage) could not be estimated. The colony, the heronries begin to decline and are average number of young per clutch seems to abandoned. The herons must then find a new be increasing in the St. Lawrence colonies and nesting site. Human disturbance and predation remaining stable elsewhere. With this relatively can also impair reproductive success and high nesting success in the St. Lawrence, result in the abandonment of a colony. Every although the number of nests seems to have 5 years, the Ministère des Forêts, de la Faune declined, the heron population should remain et des Parcs du Québec conducts a survey of stable, since herons typically lay 5 eggs and rear known colonies. In 2012, the survey found an average of 2.2 young to fledging. However, 242 active colonies, of which 171 had at least the population may be affected by other 5 occupied nests. The largest colony in Quebec factors, and long-term monitoring is needed to is located in the Grande-Île Wildlife Preserve document the trends observed. in the archipelago of Lake Saint-Pierre and Previous editions of this fact sheet provided contamination data for eggs and for young herons. However, monitoring of young was discontinued following a review of the Great Blue Heron monitoring program, and now only eggs are harvested every five years in four colonies. In 2011, the following colonies were sampled: Île aux Hérons and Grande-Île, in the fluvial section; Île aux Basques, in the lower estuary; and Île Manowin, in the Gulf. Figure 1. Location of Great Blue Heron colonies in the St. Lawrence, sections of the river and control sites outside of the river. 2 BIOLOGICAL RESOURCES WATER SEDIMENTS SHORELINES USES The colonies are visited between late April and late May. Since Great Blue Herons nest in treetops, a professional climber is hired to retrieve one egg from each nest. The eggs are placed in a padded box, which is lowered to the ground by rope. The eggs are kept cool and sent to the laboratory to be analyzed for mercury,1 PCBs,2 organochlorine pesticides (e.g., DDT3),PBDEs4 and sometimes dioxins and furans.5 Due to fluctuations in the size and presence of colonies, it is sometimes difficult to monitor the same colony over a long period. Therefore, the colonies are grouped by region (Figure 1), Great Blue Heron colony near Matagami and the contaminant concentrations presented Photo: Christine Lepage are the average concentrations for each region. © Environment and Climate Change Canada The contaminants or contaminant groups presented are the most abundant contaminants differences from region to region, both along or the contaminants of greatest concern found the St. Lawrence and when compared with in Great Blue Heron eggs. Concentrations of the control colonies located inland. PBDEs, a mercury, PCBs, DDE (the main breakdown new group of toxic substances used as flame product of DDT) and a number of other retardants, were analyzed for the first time in organochlorine pesticides have declined since Great Blue Heron eggs that had been collected this program was launched in 1991 (Figure in 2001 and 2002 (Figure 3). During this period, 3). The contaminant concentrations show few concentrations of total PBDEs in Great Blue Heron eggs were on the same order of magnitude 3.5 as those of DDE and PBDE concentrations measured 3 (11) in Herring Gull eggs from the Great Lakes. These (7) 2.5 (15) (8) (30) emerging substances pose (14) (10) concerns because they 2 (8) have similar properties to PCBs. However, they too 1.5 have clearly declined since 2001. These declines are 1 success (Number of young per nest) per young of (Number success the result of numerous 0.5 regulatory measures and Nesting voluntary phase-outs by 0 companies, both in Canada 1977-1979 1980-1983 1986-1987 1991-1993 1996-1997 2001-2002 2006-2007 2012 and around the world, Nesting period as well as the gradual Figure 2. Nesting success of Great Blue Heron (number of young per nest) in St. Lawrence colonies from 1977 to 2012 Note: Figures in parentheses indicate the number of colonies used in the calculations 3 BIOLOGICAL RESOURCES WATER SEDIMENTS SHORELINES USES 0.5 1 Mercury Mercury historic 0.4 0.8 2011 0.3 0.6 0.2 0.4 Hg (mg/kg) Hg (mg/kg)Hg 0.1 0.2 0.0 0 9 25 8 PCBs 7 20 historic 6 PCBs 2011 5 15 4 3 10 PCBs (mg/kg) 2 PCBs (mg/kg) 1 5 0 6 0 12 5 DDE 10 DDE 4 historic 3 8 2011 2 6 DDE (mg/kg)DDE 1 4 DDE (mg/kg)DDE 0 2 140 0 120 TCDD-TEQ 1200 100 1000 TCDD-TEQ 80 2001 TEQ (pg/g) 800 - 60 2006 40 600 TCDD TEQ (pg/g) 20 - 400 0 TCDD 200 800 700 PBDEs 0 600 600 500 500 pentaBDE historic (2001) 400 300 400 2011 PBDEs (ng/g) 200 300 100 0 200 Fluvial Upper Lower Freshwater Gulf (ng/g) pentaBDE 100 section estuary estuary control control 0 1991-1993 1996-1997 2001-2002 2006-2007 2011 Île aux Hérons Grande Île Île aux Basques Île Manowin Figure 3. Concentrations of mercury, PCBs (sum of 38 congeners), DDE, Figure 4. Comparison of concentrations of contaminants in Great Blue TCDD-TEQ and PBDEs (sum of 8 congeners) in Great Blue Heron eggs; Heron eggs with toxicity indices; the red lines represent the indices note the different scales Sources of indices: Blus 2011, Harris and Elliott 2011, Shore et al. 2011, Environment Canada 2010 4 BIOLOGICAL RESOURCES WATER SEDIMENTS SHORELINES USES elimination of contaminants accumulated in the considerably. These indices must be used with environment. caution, however, because they are typically based on studies conducted on other species The concentrations of the main contaminants and include an uncertainty factor. Exceedances measured in eggs collected in 2011 in the of these concentrations do not necessarily four colonies now being monitored were result in harmful effects. compared with the values measured since the beginning of the program and with toxicity 1 Mercury: Mercury is a naturally occurring element found in the Earth’s crust. About half of the mercury currently present in the indices (Figure 4). The average decline in the environment comes from human activity (such as coal burning various contaminants since the beginning and waste incineration), while the other half can be attributed to natural sources and processes. Mercury is persistent and of the program is 63% (range 41–94%) on builds up in living organisms. Île aux Hérons, 66% (36–97%) on Grande- 2 Polychlorinated biphenyls (PCBs): A class of 209 chemicals Île, 34% (41–94%) on Île aux Basques and (classified into groups ranging from monochloro- to decachloro- 59% (36–97%) on Île Manowin.
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