Oceanography | Vol. 38, No. 2
12
the ecosystem” and that these activities were “managed appro
priately such that impacts remained less significant than natural
perturbations” (Fisheries and Oceans Canada, 2010).
The EHV MPA is on the Endeavour Segment of the Juan de
Fuca Ridge, a section of the global mid-ocean ridge (MOR) sys
tem located in the Northeast Pacific Ocean off the west coast
of British Columbia. The MOR extends for 70,000 km through
out the global ocean and is where tectonic plates diverge and
new oceanic crust is formed. This spreading process results
in a permeable seafloor, allowing cold seawater to percolate
downward where it is heated by rising magma from the upper
mantle. During its subseafloor circulation, the seawater reacts
chemically with the surrounding crust and is eventually ejected
back into the ocean as mineral-laden, oxygen-depleted, and
superheated fluid. The process of mixing with cold, oxygen
ated seawater leads to a succession of rapid chemical reactions,
which form precipitates and creates the chimney-like hydrother
mal vents that are the hallmark of the Segment (Figure 2). As the
buoyant vent plume rises, the hot metal- and sulfide-rich hydro
thermal vent fluid continually reacts with the seawater to cre
ate dark, smoke-like, emissions highly enriched in Fe, S, Cu, Ca,
and Zn (Feely et al., 1987). The plume rises 200–300 m above the
seafloor, at which point it reaches a neutrally buoyant state and
spreads with the local oceanic currents as the chemical processes
continue (Coogan et al., 2017). This flux of vent fluids plays a
major role in maintaining the ocean’s chemical balance. Nearer
to the seafloor, chemosynthesis-based biological communities
utilize both the energy exchange occurring when these chemical
species mix with the oxygenated seawater and the chemical spe
cies themselves to form the basis of the hydrothermal vent eco
systems on the seafloor and in the water column (Van Dover,
2000; Burd and Thomson, 2015).
This paper provides an overview of the main geological, bio
geochemical, and physical processes at the Endeavour Segment
and their roles in regulating the biological communities and
habitat structures that host ecosystems at the vents and near the
seafloor. We describe highlights of the past 16 years of scien
tific research and monitoring enabled by the NEPTUNE sea
floor cabled observatory that support management decisions for
the MPA. Recently, the EHV MPA’s boundaries were repealed
and subsumed into the 133,017 km² Tang.ɢ̱ wan – ḥačxʷiqak –
Tsig̱ is (TḥT) MPA. This significantly expanded area is of cul
tural and economic significance to coastal Indigenous peoples
of the west coast of North America and is cooperatively man
aged by the Council of the Haida Nation, the Nuu-chah-nulth
Tribal Council, the Pacheedaht First Nation, and the Quatsino
First Nation, together with Fisheries and Oceans Canada
(Government of Canada, 2024).
THE NEPTUNE OBSERVATORY
In addition to its designation as an MPA, the Endeavour Segment
was also selected as one of the three Integrated Studies Sites for
the US National Science Foundation-funded Ridge 2000 pro
gram (Fornari et al., 2012) that attracted significant global sci
entific attention. Highlighting Endeavour’s scientific value, the
proposal for a NEPTUNE cabled observatory was successfully
funded, with the primary purposes to understand the spread
ing, subduction, and faulting of the Juan de Fuca plate, as well as
the ecosystems and oceanography off the west coast of Canada.
For the purposes of MPA management, the deep-sea observa
tory enhances observation and monitoring in the area.
FIGURE 2. This close-up view shows a black smoker chimney at the Main
Endeavour Field. Image credit: ONC and CSSF–ROPOS