DISCUSSION

Grafton Bay [Sta. KML 111/99]

Overall the biota is qualitatively similar to that in some other nearby Strait of Georgia Fjords such as Indian Arm and Jervis Inlet. However, it has a lower biodiversity and fewer species of seaweeds than in these fjords. This might be related to pollutants such as from Brittania Mines tailings and from Woodfibre (e.g., Bard, 1991, McDaniel, 1973). The absence of the wrinkled whelk, Nucella lamellosa, is likely a reflection of the impact of TBT antifouling paints as it has been reported as absent both to the west (Gibson's Landing) and east (e.g., Pt. Atkinson and Horseshoe Bay) due to this pollutant (Institute of Ocean Sciences, 1996).

The shoreline may be characterized as semi-protected rather than semi-exposed as the two sites on the south side of Bowen Island. The north facing shore would also result in greater shading and lower maximum temperatures than on south facing slopes such as station 113 and 114. The Grafton Bay site is also characterized by an abundance of under rock habitats. These are largely absent in the higher wave energy sites at Arbutus Bay (Sta. 113/99) and the Fairweather coast (Sta. 114/99).

Grafton Bay is also subject to wave action from passing standard hull ferries. According to a local upland owner, and from my own observations, this has caused considerable erosion near the high tide line.

The above factors taken together limit the utility of Grafton Bay as a control site due to the many differences between it and the south Bowen Island sites.

Bowen Bay [Sta. KML 112/99]

My brief visit to Bowen Bay was largely to observe first hand the nature of the onshore surge generated by the Pacificat Ferry. I have repeatedly observed the action of waves from standard ferries passing a short distance by Arbutus Point on Portland Island. The surge from the Pacificat at this point on Bowen Island appeared significantly stronger

and faster than those seen on Portland Island. However, the characteristics of Pacificat generated waves should be assessed under controlled, known conditions with appropriate instrumentation.

Seven of the eight species observed under rocks are either mobile or semi sessile. Six of these species would be expected to move out into tidepools or during high tide during part of the day. All could be dislodged in the open by waves of appropriate force.

The residence owner, Ardis Breeze, stated that sea stars had been common and were now gone. The surge channel faces north and would normally be considered as semi-protected from wave action both in winter and summer. The occurrence of artificially induced surging waves could have a significant impact on flora and fauna adapted to semi-protected conditions. The reports and direct observations of large logs crashing ashore can also devastating impacts on shore biota (e.g., Dayton 1971)

Fairweather coastline (Sta. KML 113/99)

My overall impression of the biota on and near the transect was of a seaweed

dominated community typical of areas with high levels of nitrates but also of areas with few or no herbivores. High nutrient levels might be expected from input by the Fraser River plume which regularly reaches the south coast of Bowen Island. I don't understand the near absence of herbivores. Following my field work, I asked a biologist with Parks Canada, Tom Tomascik, to have a look on the east coast of Tumbo Island which is similarly inundated by the Fraser River Plume. He found lots of mobile herbivores such as limpets and littorines. He also observed numerous predatory purple sea stars and wrinkled whelks. The abundance of purple sea stars is known to vary considerably from place to place and, as noted above, wrinkled whelks have been decimated by a TBT containing antifouling paint. The herbivore species in question

also occur on wave exposed shores on the west coast of Vancouver Island.

These and other mobile species such as shore crabs and tidepool fish could be dislodged and removed from the shore by wave action. A fairly large literature has developed on the impact of high wave energy on intertidal species (e.g. Vogel 1981, Koehl 1984, Denney 1988).

The effects of waves on organisms may be from the water velocity itself ; water acceleration; the drag created by these forces; the impact presssure of water; and suction. Many animals can take evasive action: limpets, chitons and sea stars lowering their profile and increasing their "suction" onto rocks; crabs and periwinkles moving into cracks and crevices. The forces of swell and storm waves develop over time which, at least, theoretically permits mobile animals to mount a defense. Winter southeasters on the southern Bowen Island shoreline would be a typical example. However, forces generated from vessel waves increase dramatically almost instantaneously which could obviate any defensive maneuvers. These sudden forces have certainly impacted the human species on the shorelines subject to Pacificat ferry waves. We don't have the same kind of direct evidence for other mobile species but their absence or near absence

is certainly suggestive. I can't think of any other compelling explanations for the paucity of mobile species (except for the special case of TBT mediated disappearance of wrinkled whelks noted above).

.

In British Columbia, as elsewhere, there are clear relationships between species community composition and wave exposure (e.g., Austin et al 1971). Some species

occurring on the semi-exposed south coast of Bowen Island would be absent or altered on wave exposed coasts. These include:

Species Wave exposed coast

sugar kelp (Laminaria saccharina) absent

rock weed (Fucus gardneri) reduced growth form to absent

blue mussel (Mytilus trossulus) limited to small size

purple sea star (Pisaster ochraceous) few to absent (fully exposed coast)

The tattered condition of sugar kelp on the Fairweather coastline is atypical for this species in summer although this condition regularly occurs elsewhere in winter, at least in part, due to wave action.

In summary, the absence of certain species and the poor condition of a wave exposure indicator species is strongly suggestive of some unnatural impact. The waves generated by Pacificat ferries are a prime candidate as a causative agent. This coastline has also been subject to waves from regular ferries for many years.

Arbutus Bay (Sta. KML 114/99)

Muddy sand beach

The very impoverished macrofauna might be correlated with several factors. The freshwater run-off from Josephine Creek extended down the transect line. The volume of run-off would not be expected to a major impact in limiting e.g., clams based on observations for similar run-off on a sand flat and estuary in Vancouver Island. Some species can shut down and close-up in fresh water, then open, and begin feeding and respiring as seawater floods in with the tide. However, I cannot preclude the possibility that major and continuous runoff in the winter might limit the macrobiota at least at higher tide levels.

Wave energy is a more likely candidate in limiting the biota. The beach, while facing southeast, is still subject to fierce winter storm waves generated from southeasterlies over a long fetch comparable to that for the Fairweather coastline about a km to the west.

According to Gary Ander such storms last winter had a devastating impact on the berm

and foreshore above the beach. Winter storms would be expected to remove sand and redeposit it offshore. The sand would gradually move back onshore during the summer (e.g., Bascom, 1964). Some macrobiota which settled in the summer would be exposed and perhaps carried offshore during the winter. However, some species might burrow to such sufficient depths by winter that they would escape being exposed and dislodged.

Wave energy from ferries, and particularly catamaran waves could modify this pattern. A shell sand beach at Arbutus Pt on Portland Island has a good population of butter clams. It is not subject to major winter storms but is subject to significant wave action from normal ferries. Would this clam population be affected by catamaran generated waves ? Unfortunately, I am unaware of any data to support or refute a potential impact.

Bedrock slope

The similarity of the biota here to that at the Fairweather coastline station is support that the biotic impoverishment, particularly of mobile species, is not due to some immediately local factor.

Studies of ferry impacts in other regions

An exhaustive search of the literature on ferry wave shore impacts was beyond the terms of reference for this study. However, assessments from a few studies are noted below.

Östman and Rönnberg (1991) observed changes in rocky pool biota resulting from ferry wakes. Fagerholm (1975, 1978) and Rönnberg (1981) reported that the biomasses and numbers of species of seaweeds and invertebrates are reduced on shores facing ferry routes in southwestern Finland.

One study on impacts of waves from catamarans was made by BioAquatics International

(1999) in Rich Passage in Puget Sound south of Bainbridge Island. Unlike the south coast of Bowen Island, the shorelines of Rich Passage are at least semi-protected from

wind generated waves. They note that during the winter daylight high tides, the waves generated by catamarans overtop existing bulkheads and kill or damage terrestrial maritime vegetation. On the south coast of Bowen Island in winter the wind generated storms may overshadow wave impacts from catamarans. However, during the summer non-storm season some of the catamaran generated wave impacts may become a paramount factor in biological community structure. The BioAquatics study has demonstrated movement of cobble size rocks and generation of turbidity from Catamaran wave action. Increase in turbidity was evident during Catamaran generated wave events on Bowen; however, the impacts are not clear. Bioaquatics points out that leaf-like seaweeds will be affected by wave action. I have noted that the leaf-like sugar kelp (Laminaria saccharina) on the south coast of Bowen Island is torn and tattered; and that, normally, this would not be expected until winter storms developed. The authors also note that barnacles were removed and recruitment affected by erosion and/or abrasion by Catamaran generated waves and movement of cobbles. Similar effects might be overshadowed by storm waves during the winter on the exposed southern Coast of Bowen Island but could be a significant additional impact during the summer and in protected areas such as the south end of Bowen Bay. Dr. Dan Cheney enlarged on this report in a Supplemental Declaration to the Superior Court of Washington (Cheney 1999). He notes that there is a significant likelihood that cobbles and boulders had been moved into shallower water by catamaran waves. Associated species moved out of their normal habitat would likely not survive. Dr. Cheney noted a large amount of drift seaweed on the beach which was likely torn loose by catamaran waves. I have observed a similar major concentration of drift seaweeds in areas subject to wave action from standard ferries (on Chad and Portland Islands). I did not observe large amounts of drift seaweeds at the Bowen Island station; however, residents should be asked if they observed any increase in drift seaweed immediately after the Pacificat ferries began operating in July.

RECOMMENDATIONS

  1. Document changes in sailing patterns of Pacificats since initiating service in July 1999.
  2. Collate any information on perceived changes in wave patterns on the shore-line which might be related to changes in sailing patterns.L>
  3. Obtain copies of impact studies commissioned by BC Ferries and assess them.
  4. Revisit the stations in August 2000 to assess any changes in biota.
  5. Compare the physical characteristics of waves generated from various kinds of storms, regular ferries, and catamaran ferries.
  6. Experimentally demonstrate the effects of waves comparable to those generated by Pacificats on the macrobiota and on varies types of beaches.
  7. Introduce marked mobile animals (e.g., limpets, periwinkles and seastars) to habitats subject to catamaran waves and to control sites and assess subsequent fate
  8. Assess habitats in wave protected or semi-protected areas which are (or better) will be subject to wave action from Pacificats.

REFERENCES

Austin, W.C., L.D. Druehl, & S.B.Haven. 1971. Bamfield Survey: Marine habitats and biota. Bamfield Marine Station Rpt. #2:33p.

Bard, S. 1991MS. The effect of pulp mill pollution on intertidal community structure and diversity in the Strait of Georgia. Unpublished MS but available from Bill Austin. (It may be published as of 1999)

Bascom, W. 1964. Waves and beaches. The dynamics of the ocean surface. Doubleday, Garden City, NY. 267p.

BioAquatics International. 1999. Biological and shoreline survey Rich Passage, Washington. Prepared for Hagens & Berman, Seattle, WA. 15p.

Cheney, D. 1999. Supplemental Declaration of Dan Cheney, Ph.D. to Superior Court of Washington in and for Kitsap County. No. 99-2-01161-1.

Dayton, P.K. 1971. Competition, disturbance, and community organization: The provision and subsequent utilization of space in a rocky intertidal community. Ecological Monographs 41:351-389.

Denny, M.W. 1988. Biology and the mechanics of the wave-swept environment. Princeton Univ. Press, Princeton, NJ. 329p.

Fagerholm, H. –P. 1975. The effects of ferry traffic on the rocky shore macrofauna in the southern Åland archipelago: 1. The Cladophora zone. Merentutkimuslaitokson Julkaisu/Havsforskningsinstitutets Skrift 239:331-337. [NOT SEEN]

Fagerholm, H. –P. 1978. The effects of ferry traffic on the rocky shore macrofauna in the southern Åland archipelago in the northern Baltic. 2. The Fucus zone (a quantitative study). Kieler Meeresforschungen Sonderheft 4:130-137. [NOT SEEN]

Koehl, M.A.R. 1984. How do benthic organisms withstand moving water? Amer. Zool., 24:57-70.

McDaniel, N.G. 1973. A survey of the benthic macroinvertebrate fauna and solid pollutants in Howe Sound. Fisheries Res.. Bd. Tech. Rpt. 385. 64p.

Östman, M. & O. Rönnberg. 1991. Effects of ships' waves on rock-pools in the Åland Archipelago, Northern Baltic Sea. Sarsia 76:125-132.

Rönnberg, O. 1981. Traffic effects on rocky-shore algae in the Archipelago Sea, SW Finland. Acta Academiae Aboensis, Ser. B 41(3):1-86. [NOT SEEN]

Vogel, S. 1981. Life in moving fluids. The physical biology of flow. Princeton Univ. Press, Princeton, NJ. 352p.