June 2025

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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

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