Arthur C. Mathieson

Developing Porphyra/salmon integrated aquaculture for bioremediation and diversification of the aquaculture industry

For rapid growth and appropriate pigmentation,Porphyra requires the constant availability of nutrients, especially in summer when temperate waters are generally nutrient depleted. Cultivation near salmon cages allows the alleviation of this seasonal depletion by using the significant loading of fishf arms, which is then valued (wastes become fertilisers) and managed (competition for nutrients between desirable algal crops and problem species associated with severe disturbances). Porphyra,being an extremely efficient nutrient pump, is an excellent candidate for integrated aquaculture for bioremediation and economic diversification. Frequent harvesting provides for constant removal of significant quantities of nutrients from coastal waters, and for production of seaweeds of commercial value. The production of P. yezoensis being limited in the Gulf of Maine, an assessment of the potential of seven native north-west Atlantic Porphyra species is presently in progress. To enable the production of conchospores for net seeding, the phenology of these species and the conditions for their vegetative conchocelis exponential growth, conchosporangium induction, and conchospore maturation were determined. The development of integrated aquaculture systems is a positive initiative for optimising the efficiency of aquaculture operations, while maintaining the health of coastal waters.

Ecological studies of economic red algae. v. growth and reproduction of natural and harvested populations of Chondrus crispus Stackhouse in New Hampshire

Abstract The seasonal growth, reproduction, and occurrence of Chondrus crispus Stackhouse have been determined at four New Hampshire locations and correlated with seasonal and spatial variations of surface salinity, temperature, and nutrients. Spring growth was initiated in March and April. Chondrus populations exhibited their maximum size and biomass during the late summer-fall. The period of fastest growth coincided with increasing summer temperature and day-length. Seasonal and spatial differences of reproduction were noted at the four sites. Cystocarpic plants were usually abundant during the late summer-winter. Tetrasporic plants showed a sporadic occurrence and were less common than cystocarpic plants — particularly at the more sheltered sites. The most extensive populations of Chondrus occur on the open coast i.e., on massive outcrops and boulders in the mid subtidal zone (−3 to −5 m below M.L.W.). The re-growth and reproduction of Chondrus populations after harvesting is dependent on the time and initial level of harvesting. Carefully and moderately harvested plots of the summer allowed re-growth to control levels of biomass in 5 to 6 months; the same quadrats were at or near (80 %) of the control values of reproduction after 9 months. Winter harvests had a more prolonged effect on re-growth and reproduction. Intertidal quadrats that were sequentially denuded for 22 months showed a biomass equal to the controls after 18 months of re-growth; reproductive structures were found after 13 or more months of re-growth.

Seasonal growth and reproduction of estuarine fucoid algae in New England

Estuarine populations of Ascophyllum nodosum (L.) Le Jolis and Fucus vesiculosus L. var. spiralis Farlow from the Piscataqua River of the Great Bay Estuary System (New Hampshire-Maine) showed their maximum growth during the spring and fall of two consecutive years. The maximum growth rates (in terms of elongation) for Ascophyllum and Fucus were 3.5 and 3.6 cm/month, respectively, during 1973, and 3.2 and 2.3 cm/month in 1974. The average length of whole Fucus fronds showed a trend towards longer plants during the early spring and late summer-fall, while the average weight was significantly greater in the spring and early summer. Ascophyllum showed a distinct reproductive periodicity, with a maximum in March or April of both years; after the spring period of maximum reproduction, the receptacles dehisced simultaneously and the plants were vegetative during the summer. The reproductive periodicity of Fucus was not so distinct as that of Ascophyllum; even so, its maximum reproduction was in April of both years. The level of reproduction for Ascophyllum populations was three times greater in 1974 than in 1973. The reproduction and growth of the two fucoid algae are related to seasonal variations in temperature and light.

Ecological studies of economic red algae. I. Photosynthesis and respiration of Chondrus crispus Stackhouse and Gigartina stellata (Stackhouse) Batters

Abstract The photosynthesis and respiration of Chondrus crispus Stackhouse and Gigartina stellata (Stackhouse) Batters are recorded under a variety of light intensities, temperatures, salinities, and degrees of desiccation. The apparent photosynthesis (uncorrected for plant respiration) of C. crispus is light-saturated at ~ 1000 ft-c, that of G. stellata at ~2100 ft-c. The optimal temperature for photosynthesis in both species is ~20 °C, but they have a high photosynthetic capacity over a wide range of temperatures. The respiration of C. crispus and G. stellata is relatively uniform from 8–20 °C. Both species have maximum photosynthesis/respiration ratios at 20 °C. C. crispus showed its maximum photosynthesis and minimum respiration at a salinity of 24‰; G. stellata exhibited maximum photosynthetic and reduced respiration rates at 40%.. The apparent photosynthesis and respiration of C. crispus are adversely affected by a high degree of dehydration, while G. stellata is more flexible. The local abundance and distribution of C. crispus and G. stellata are correlated with their photosynthetic responses.

Reproductive Phenology and Growth of Gracilaria tikvahiae McLachlan (Gigartinales, Rhodophyta) in the Great Bay Estuary, New Hampshire

The reproductive phenology of Gracilaria tikvahiae McLachlan from the Great Bay Estuary, New Hampshire, U. S. A., was evaluated monthly during May 1976 to October 1977. The plants were vegetative throughout most of the study period. However, discrete maxima of tetrasporic and spermatangial plants occurred during June—July, while cystocarpic plants were maximal during July—August. The in situ growth of G. tikvahiae, measured during April 1978 to August 1979, was maximal during June—August, and minimal during the winter. The growth of G. tikvahiae was most strongly correlated with water temperature, while seasonal variations of surface irradiance and dissolved inorganic nitrogen were not significantly correlated to the growth cycle.

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

The high degree of morphological plasticity displayed by species of the brown algal genus Fucus L. is well documented. Such variation is especially pronounced for those estuarine taxa lacking holdfasts (termed ecads) that often bear little resemblance to the attached species from which they are derived. To better understand the systematics of salt marsh fucoids, we developed a suite of four microsatellite‐containing loci capable of distinguishing between F. vesiculosus L. and F. spiralis L. The genetic markers were used to determine the relationships of the fucoid ecads F. vesiculosus ecad volubilis (Hudson) Turner and a muscoides‐like Fucus in the Brave Boat Harbor (ME, USA) estuary. Ecad populations had 2‐ to 3‐fold higher levels of heterozygosity than attached populations of F. vesiculosus and F. spiralis. Further, ecads were “intermediate” between F. vesiculosus and F. spiralis in their allele frequencies and genotype composition. Our data indicate that populations of muscoides‐like Fucus in Brave Boat Harbor mainly consist of F1 hybrids between F. vesiculosus and F. spiralis, whereas F. vesiculosus ecad volubilis may arise through backcrosses between F. vesiculosus and other fertile hybrids. Finally, our data support the hypothesis that introgression has occurred between attached populations of F. vesiculosus and F. spiralis.

Seasonal influx and decomposition of autochthonous macrophyte litter in a north temperate estuary

An 18-month study was undertaken to determine the seasonal contribution and detrital processing of autochthonous plant litter in the Great Bay Estuary System of New-Hampshire-Maine, USA and adjacent open coast. Four species were studied: the halophytes, Spartina alterniflora Loisel. and Zostera marina L. and the seaweeds, Ascophyllum nodosum (L.) Le Jolis and Fucus vesiculosus L. v. spiralis Farlow. Monthly strand line collections at estuarine and open coastal sites provided information on the seasonal influx of litter derived from each species. Detrital inputs from S. alterniflora and Z. marina were maximal in the spring and summer, respectively. Seaweed litter was abundant (35 to 85% of the total strand line) throughout the year. The seaweeds contributed 1 to 3 times as much detrital material as the vascular plants within the Estuary, and 50 times as much on the open coast. In situ measurements of decomposition, using nylon, mesh bags, were made for each species under several environmental conditions. Seaweeds decomposed 3 to 10 times faster than vascular plant litter under similar conditions. Decomposition rates and changes in the nutrient content of litter were dependent on surrounding environmental conditions. Continual nutrient depletion occurred in litter within the strand line. Nitrogen and phosphorus enrichment were observed under submerged conditions and were attributed to microbial activity and rapid leaching of carbonaceous substrates. A computer simulation model was developed to validate the field data and to predict seasonal detrital carbon input by each species. The significance of autochthonous input is discussed in relation to other detrital sources.

Identification of north-western Atlantic Porphyra (Bangiaceae, Bangiales) based on sequence variation in nuclear SSU and plastid rbcL genes

Abstract Six species of Porphyra have commonly been recognized in the north-western Atlantic from Long Island Sound to the Canadian Maritimes: P. amplissima, P. leucosticra, P. linearis, P. miniata, P. purpurea, and P. umbilicalis. Distinguishing them with certainty has been problematic. A DNA-based system of molecular identification was developed using partial sequences of the nuclear small subunit ribosomal RNA gene (SSU) or the plastid ribulose-1,5-bisphosphate carboxylase–oxygenase large subunit gene (rbcL). Multiple samples of each taxon were surveyed for intraspecific variation. Intraspecific SSU divergences for Porphyra ‘leucosticta’, P. ‘miniata’, P. ‘umbilicalis’, and P. ‘purpurea’ ranged from 0% to 1%. There was more variation for P. ‘amplissima’ (0–2.1%) and P. ‘linearis’ (0–3.5%); however, each taxon was monophyletic. No intraspecific differences were observed for these taxa in rbcL (one to eight samples per taxon). These sequences were compared with P. yezoensis U51, introduced to Maine, and with P. ‘dioica’, a north-east Atlantic Porphyra easily confused with P. ‘purpurea’. To discriminate between P. ‘purpurea’, P. ‘umbilicalis’, and P. ‘leucosticta’, SSU variation was used to design primers for the Allele-Specific Polymerase Chain Reaction™. With molecular tools, we could classify over 80% of the monostromatic specimens surveyed, but the residue of unidentifiable specimens may indicate the existence of further monostromatic species in the north-west Atlantic. Porphyra ‘purpurea’ was found to occur further south than previously recorded. A morphologically cryptic Porphyra was discovered at Herring Cove, Nova Scotia, Canada.† Phylogenetic analyses using SSU or rbcL sequences showed ‘soft incongruence’ between gene trees, i.e. the topologies of the phylograms were similar but not identical, with only weak to moderate bootstrap support for the nodes that differed. Both trees strongly supported a clade including P. ‘purpurea’, P. ‘umbilicalis’, P. ‘linearis’, and P. ‘dioica’. Porphyra sp. Herring Cove was allied with the remaining Porphyra taxa in the SSU tree. The rbcL phylogeny was less well resolved, consisting of a polytomy of a P. ‘purpurea’–P. ‘umbilicalis’–P. ‘linearis’–P. ‘dioica’ clade, Porphyra sp. Herring Cove, a clade comprising P. ‘amplissima’ and P. ‘miniata’, and a P. ‘suborbiculata’–P. ‘leucosticta’–P. yezoensis clade.

Physiological studies of subtidal red algae

The net photosynthesis of the subtidal red algae Euthora cristata (C. Agardh) J. Agardh, Phycodrys rubens (L. ) Batters, Phyllophora truncata (Pallas) Newroth et Taylor and Ptilota serrata Kutzing were determined under a variety of different light and temperature regimes. The optimal light requirements for net photosynthesis of the species are relatively low, mostly ranging from 465 to 747 ft-c at 5 ° and 15 °C. Seasonal and spatial differences were found in the photosynthesis-light responses of Phyllophora truncata and Ptilota serrata; winter plants exhibited lower light optima for net photosynthesis than spring plants. Deep-water populations of Ptilota showed lower light optima and reduced net photosynthesis as compared with shallow subtidal populations. Summer plants of Euthora cristata, Phycodrys rubens and Phyllophora truncata showed a greater tolerance to high temperatures and higher temperature optima than winter plants. It is suggested that optimal temperature and light requirements of seaweeds are adjusted in an adaptive fashion to the environmental regimes of their habitats. The temperature requirements of the four species are discussed in relation to their local estuarine distributions in New England; eurythermal species have the widest estuarine distributions. Cystocarpic and tetrasporic plants of Euthora cristata and Ptilota serrata show differential physiological responses and vertical distributions. The significance of higher rates of net photosynthesis and lower light optima are discussed in relation to vertical stratification of different generations.

An ecological study of fucus spiralis L.

Abstract An ecological study of Fucus spiralis L. has been made at Jaffrey Point, Newcastle, New Hampshire and the adjacent Great Bay Estuary System from 1972–1975. The distribution, growth, reproductive periodicity, attrition and longevity of the plants are described in relation to a variety of environmental factors. F. spiralis shows a broad but discontinuous estuarine distribution within the Great Bay Estuary System. The presence or absence of appropriate substrata is considered to be a factor determining its discontinuous distribution, since it is usually associated with metasedimentary or metavolcanic rock outcrops. The maximum growth and reproduction of F. spiralis are during the summer. The summer growth rates ranged from 1.9 to 2.8 cm/month while the average growth rate throughout the year was 1.2 cm/month. F. spiralis populations showed two periods of major attrition, namely, during the winter and summer. The average longevity of F. spiralis plants is ≈ 2 yr. The F. spiralis zone lies in the uppermost intertidal area between +2.12 and +2.31 m above M.L.W. There is a micro-stratification of biomass, stature, and reproductive activity within this zone. Average plant weight, length, and fertility tend to decrease with increasing elevation.