Trophic Status of Casco Bay, Maine, as Delineated by Seaweed Diversity and Tissue Analysis

Primary tabs

Project Type: 
Project Number: 
Inception Date: 
Completion Date: 
Theme Area: 
Coastal Ecosystem and Public Health


Arthur Mathieson UNH - Jackson Estuarine Lab Principal Investigator
Christopher Neefus UNH - Department of Biological Sciences Co-Principal Investigator
Clinton Dawes University of South Florida Co-Principal Investigator

Students Involved:

Jon Larsen UNH - Department of Biological Sciences
Andrew West UNH - Graduate Program in Genetics
Brian Teasdale UNH - Department of Biological Sciences
Danielle Friel Cain UNH - Graduate Program in Genetics

Casco Bay is the second largest bay in Maine and, because of its size, complexity and habitat diversity, provides a variety of critical environments for juvenile and adult fish and birds. Unfortunately, the Bay has experienced diverse sources of toxic pollution (polyaromatic hydrocarbons, heavy metals, sewer discharges, etc.), which have degraded wildlife habitats and diminished water quality.

A number of organizations have come together to develop a Casco Bay Plan designed to reverse this degradation. This research will contribute to that effort by characterizing seaweed populations from estuarine and open coastal sites in the Bay and evaluating possible long-term changes, by evaluating several recent changes in seaweed communities due to human introductions and/or anthropogenic effects, and by analyzing seaweed tissue for PAH, trace metals and nutrient pollution in order to compare polluted and pristine sites.


The primary objectives of our proposed studies are three-fold:

1) Characterize seaweed populations from estuarine and open coastal sites in Casco Bay and evaluate possible long term changes (early 1900s versus present-day) of seaweed biodiversity (i.e., species richness and composition) from a variety of "natural" and "stressed" environments using historical records by F. S. Collins

2) Evaluate several recent changes (50 years or less) in seaweed communities due to human introductions and/or anthropogenic effects, plus identify indicator species for polluted and "pristine" areas that can be monitored by coastal managers

3) Analyze tissue contents in two broadly cosmopolitan seaweed taxa (i.e., Ascophyllum nodosum and Ulva lactuca) for PAH, trace metal (Pb, Hg and chromates) and nutrient pollution (cf. Hardwick-Witman & Mathieson 1986; Levine 1984; Lyngby 1990; Phillips 1977; Rueness 1973; Whitton 1984) that will be used to compare indicator species from polluted and more "pristine sites." Transplants of A. nodosum from clean to polluted sites will also be analyzed in order to assess the speed of metal and nutrient uptake. Similar assessments of tissue contents in historical herbarium samples will be made in order to provide a timeline for pollution events.


Seasonal collections of the dominant seaweed populations at approximately 20 sites within Casco Bay will be made from the summer of 2001 through the spring of 2003. Seaweed samples will be obtained from diverse coastal, estuarine and riverine sites that are currently being sampled by the Friends of Casco Bay and previously evaluated by F. S. Collins, including various sites on the Fore, Harraseeket, New Meadows, Presumscot and Royal Rivers.

Seaweed samples from different substrata types (rock outcrops, boulders, breakwaters and sandy-muddy areas) at each site will be obtained, as well as at habitats with varying hydrographic conditions (temperature and salinity). Both of these physical factors are of critical importance in determining estuarine algal populations (Hardy et al. 1993; Mathieson and Fralick 1973; Mathieson and Hehre 1986; Mathieson and Penniman 1986b; Wilkinson 1980).

Overall, the methods of collection, identification and processing of samples will be similar to those outlined by Hehre and Mathieson (1970) and Mathieson et al. (1981, 1996, 1998), with representative samples of all conspicuous intertidal and subtidal specimens being collected at each site. A complete set of herbarium voucher specimens (i.e., each taxon/site) will be prepared and deposited at the University of New Hampshire (NHA) in order to document these biodiversity patterns. Although Taylor (1957) will be the primary source of identification, other recent monographs will be employed for nomenclatural changes (cf. Bird and McLachlan 1992; Burrows 1991; Dixon and Irvine 1977; Fletcher 1987; Irvine 1983; Irvine and Chamberlain 1994; Maggs and Hommersand 1993; Mathieson et al. 1981, 1993; Mathieson and Hehre 1986; Prud'homme van Reine 1982; Schneider and Searles 1991; Sears 1998; South and Tittley 1986; Villalard-Bohnsack 1995).


The study will evaluate whether present-day seaweed biodiversity within Casco Bay, Maine, has changed significantly since earlier (1911) assessments by F.C. Collins, particularly within the "industrial corridor" of the Fore River. The use of biodiversity and bioassay data will allow coastal managers to identify anthropogenic impacts. Bioassay evaluations of in situ, transplanted, and historical herbarium samples of Ascophyllum nodosum and Ulva lactuca will evaluate patterns of spatial and historical pollution within Casco Bay.

Assess the success of meeting each objective identified in the project proposal

(a) To characterize seaweed populations from estuarine and open coastal sites in Casco Bay and possible long term changes (early 1900s versus present-day) of seaweed biodiversity (species richness and composition) from a variety of "natural" and "stressed" environments using historical records by Frank Shipley Collins.
An evaluation of recent and historical collections dating back to the early 1900s show that Casco Bay's flora consists of 208 taxa (53 Chlorophyta, 72 Phaeophyta, and 83 Rhodophyta). In previous studies by F. S. Collins (1911) 174 taxa were recorded, while 167 taxa were found during recent sampling. A comparison of the two time periods shows a 79.8% percent similarity; some plants have apparently disappeared (or are very rare) and others are newly recorded. Several of the newly collected seaweeds represent species that are most common in estuarine and shallow embayments and have southern warm-water affinities (e.g. Hummia onusta, Striaria attenuata, Callithamnion corymbosum, Ceramium cimbricum, Chondria baileyana, Polysiphonia denudata, P. elongata, and Spyridia filamentosa); others represent introduced taxa from different geographies, including Codium fragile ssp. tomentosoides, Ulonema rhizophorum, Bonnemaisonia hamifera, Dumontia contorta, Lomentaria clavellosa, Porphyra yezoensis f. yezoensis, and "Trailliella intricata."
(b) To evaluate several recent changes (50 years or less) in seaweed communities due to human introductions and/or anthropogenic effects, plus identify indicator species for "polluted" and "pristine" areas that can be monitored by coastal managers.
Comparisons of historical and present-day floras at two specific sites in Harpswell, Maine, showed that the percent similarity values were lower and ranged from 41.5 % at Basin Cove to 48.9% at Potts Point. At the former site enhanced water motion and the loss of a tidal dam caused increased/altered species composition, while anthropogenic impacts due to a lobster pound diminished the flora at the latter site. Historical floristic comparisons from six other geographies (Helgoland, Germany, the North Adriatic Sea, Denmark, Mount Desert Island, Maine, southern California, and the Florida Keys) were evaluated in order to compare the stability of Casco Bay's flora, as well as possible localized stress due to oil pollution. Casco Bay's seaweed flora is dominated by many annuals (i.e. 118 versus 87 perennial taxa), reflecting its seasonally dynamic habitats and pronounced temperature fluctuations. Annuals or opportunistic forms also dominate the oil impacted Fore River/Portland Harbor area.
(c) To analyze tissue contents in two broadly cosmopolitan seaweed taxa (i.e. Ascophyllum nodosum and Ulva lactuca) for PAH, trace metals (Pb, Hg & chromates) and nutrient pollution used to compare species from "pristine" sites.
Tissue analysis showed a pronounced enhancement of several trace metals within the Fore River/Portland Harbor area, which is a major terminus for agricultural and fishing products, a vital rail junction, and a major center for crude oil transport to refineries in Canada. Unfortunately, the transport of petroleum products has lead to a number of large and small oil spills, and has caused a diminished flora consisting of several "green tide" or opportunistic green algal taxa. A comparison is presently being made between this seaweed data and fish and sediment records within the Bay, particularly Portland Harbor and the eastern reaches of Casco Bay within the Kennebec- Androscoggin watershed.
Highlight findings that would be generally accepted as significant and indicate:
Comparisons of historical (early 1900s) and present-day floras within Casco Bay were only possible because of the presence of detailed collections and diaries made by F. S. Collins during the early 1900s. Overall, the Bay's flora during the past 100 years shows a much higher similarity (~ 80%) than many areas of the world, which have been badly impacted (only 28-38% similarity) during much shorter periods of 30-60 years - e.g. the North Adriatic Sea, several Danish fjords, the Florida Keys, southern California, etc. On the other hand some localized areas in Casco Bay have been badly impacted by oil transport (Portland Harbor) or "foot traffic" associated with lobster pounds (e.g. Potts Point), causing diminished % similarities. The presence of several introduced Asiatic Porphyra taxa within Portland Harbor and the Harpswell area also confirms the role of man in their transportation via shipping and diverse shellfish aquaculture actitivies.


Available from the National Sea Grant Library (use NHU number to search) or NH Sea Grant

Journal Article

  • Mathieson, A., C. Dawes, E. Hehre and L. Harris (2009). Floristic studies of seaweeds from Cobscook Bay, Maine. Northeastern Naturalist 16(Monograph 5):1-48, November 2009.
  • Neefus, C., A. Mathieson, A. Klein, B. Teasdale, T. Bray and C. Yarish (2002). "Porphyra birdiae sp. nov." (Bangiales, Rhodophyta): A new species from the northwest Atlantic. Algae 17(4):203-216.
  • Klein, A., A. Mathieson, C. Neefus, D. Cain, H. Taylor, B. Teasdale, A. West, E. Hehre, J. Brodie, C. Yarish and A. Wallace (2003). Identification of Northwestern Atlantic "Porphyra" (Bangiaceae, Bangiales) based on sequence variation in nuclear SSU and plastic rbcL genes. Phycologia 42(2):109-122.
  • Teasdale, B., A. West, H. Taylor and A. Klein (2002). A simple restriction fragment length polymorphism (RFLP) assay to discriminate common "Porphyra" (Bangiophyceae, Rhodophyta) taxa from the Northwest Atlantic. Journal of Applied Phycology 14(4):293-298.
  • Wallace, A., A. Klein and A. Mathieson (2004). Determining the affinities of salt marsh fucoids using microsatellite markers: evidence of hybridization and introgression between two species of "Fucus" (Phaeophyta) in a Maine estuary. Journal of Phycology 40:1013-1027, 2004.
  • Mathieson, A., C. Dawes, A. Wallace and A. Klein (2006). Distribution, morphology, and genetic affinities of dwarf embeded "Fucus" populations from the Northwest Atlantic Ocean. Botanica Marina 49:283-303, 2006.
  • Brodie, J., I. Bartsch, C. Neefus, S. Orfanidis, T. Bray and A. Mathieson (2007). New insights into the cryptic diversity of the North Atlantic-Mediterranean "Porphyra leucosticta" complex: "P. olivii" sp. nov. and "P. rosengurttii" (Bangiales, Rhodophyta). European Journal of Phycology 42(1):3-28, 2007.
  • Mathieson, A., E. Hehre, C. Dawes and C. Neefus (2008). An historical comparison of seaweed populations from Casco Bay, Maine. Rhodora 110(941):1-102, Winter 2008.


  • Marine Invaders in the Northeast: rapid assessment survey of non-native and native marine species of floating dock communities, August 2003 (2005). J. Pederson, R. Bullock, J. Carlton, J. Dijkstra, N. Dobroski, P. Dyrynda, R. Fisher, L. Harris, N. Hobbs, G. Lambert, E. Lazo-Wa and A. Mathieson. MIT Sea Grant College Program Pub. No. 05-3, 40 pp.


  • Bray, T. (2006). A molecular and morphological investigation of the red seaweed genus "Porphyra" (Bangiales, Rhodophyta) in the Northwest Atlantic. Doctoral dissertation, University of New Hampshire.

Book Chapter

  • Hooper, R.G., A.C. Mathieson and R.T. Wilce (2002). Geographic distributions of marine algae along the Northeastern Coast of North America. NEAS Keys to Benthic Marine Algae of the Northeastern Coast of North America from Long Island Sound to the Strait of Bele Isle, 2nd ed. Contribution No. 2, James Sears, ed., pp. 133-136. Northeast Algal Society, Dartmouth, Mass.