MREAC's interest is in the Miramichi watershed and estuarine environment. This is a huge diverse area (13,465 sq. km). The freshwater and estuarine environments are obvious divisions that have very different dynamics and biota.
The mouth of the Miramichi River in N.B. is a drowned river valley. This term implies that sea level is (and has been) rising relative to the level of the land, the river mouth thus flooded or 'drowned' in salt water. From the channel that opens Miramichi Inner Bay into the Northumberland Strait to the head of tide at Quarryville is 71km. The estuary is thus strongly influenced by diurnal(twice daily) tidal cycles. This has created an extensive estuarine environment that is over 300 sq. km. in area. The estuary is sheltered behind barrier islands that protect it from the full force of storm waves generated in the Gulf of St. Lawrence.
In this sheltered setting, the estuary is a shallow settling pond for material originating from three sources; surrounding lands, the freshwater drainage basin, and the marine environment off-shore. As a result of these influences the estuary is a very productive environment. Organic materials transported from land, freshwater and saltwater environments are at the base of a food chain that sustains remarkable populations of marine plants and animals. The variety of life is limited in estuaries by inherent stresses or extremes that select for species that are either migrant or tolerant to these conditions.
The Miramichi River estuary is no exception in this. The productivity of Miramichi Inner Bay is significant due to its size, covering over 300 sq. km. Miramichi Inner Bay receives the drainage from not only the Miramichi River, but from the Burnt Church River, Bartibog River, Black River, Baie du Vin River, and a number of lesser streams. All of these smaller watersheds have been included in MREAC's area of interest.
Like the boxer who has learned to "role with the punches" the estuarine is elastic in response to the extremes of its environment. Extreme flows from the rivers may result in dramatic changes in both salt content (salinities) and in the deep water channel that snakes through the Inner Bay. Severe storms, especially 'nor'easters', may radically change the configuration of the protective sand built barrier islands, even breaking through in new channels or relocating the old. This fluid nature of the estuarine system is recognized as the key to the successful maintenance of this highly productive environment.
With the exception of the deeper water channels, the Inner Bay is relatively shallow with an average depth of 4 meters. The channel depth by comparison averages 6 meters reaching depths over 10 meters. Normal tidal range is close to 1 meter with a diurnal flow of two highs and two lows each day. Storm conditions can result in extremes of both high and low tides, often dictated by wind direction. This shallow large estuary is readily warmed under the summer sun and the shallows allows light to penetrate and promote photosynthesis. This primary productivity in plant life is the base of an intricate food chain.
Protected behind the barrier beaches, the Miramichi Inner Bay is sheltered from the damage and turmoil of high energy on the coastal shoreline. In this relative peace, the estuary is a sediment trap, a nutrient trap, and a trap for some undesirable impacts from land and water sources. This system supports a very valuable commercial fishery including several species of fish and shellfish. Many of the coastal communities are very dependent on the economic value provided through these resources.
DDT spraying impacts in the 1950's and 60's had profound effects. A residue of this spray is, in part, resident today in the sediment deposits of the Miramichi Inner Bay. Heavy metals, from decades of base metal mining on the Tomogonops River and organochlorines from the pulp and paper mills at the head of the salt wedge, add to the potential, albeit apparently latent problems entrapped in sediment layers.
Despite its limited overall size, as compared to the rest of the watershed, the Miramichi estuary is critically important habitat. Most of the human population, most industrial and commercial activity takes place on its edge. Many of MREAC's concerns are, likewise, concentrated here in the Miramichi estuary.
The meander length of the Miramichi River is 250 km. This world renown river drains almost one quarter of the province of New Brunswick. The major tributaries comprising the Miramichi system are; the Northwest Miramichi, North Sevogle, South Sevogle, Little Southwest Miramichi, Renous, Dungarvon, Bartholomew, Barnaby, Cains, Taxis, and Southwest Miramichi enter the main branches, more depending on how you count. Most of the area is uninhabited woodlands. Much of this woodland is harvested for wood product, whether for lumber or pulp and paper. In the north of the watershed, located on the smaller Tomogonops River tributary, mineral resources resulted base metal mining, extracting zinc, copper and lead, closed and decommissioned in 2000.
Atlantic Salmon and trout fishing have made the reputation of these freshwater rivers. An international clientele frequent the lodges and camps that dot these many branches. Despite widespread declines in fish stock the Miramichi still supports an economically important recreational fishery. Annual stock assessments by DFO staff show a significant annual run of Atlantic Salmon returning to the Miramichi.