Formation of a Fouling Community on Substrates for Cultivation of the Kelp Laminaria japonica

The materials of the present research were samples of fouling from the ropes used for the cultivation of Laminaria japonica at three kelp farms in Primorye: Anna (Rifovaya Bay, Peter the Great Bay), the Glazkovka experimental farm (Glazkovka, Kit Bay), and Kamenka (Veselaya Inlet, Oprichnik Bay). Sampling was performed using SCUBA. The abundance was calculated per running meter of substrate.

RESULTS AND DISCUSSION

A total of 241 species of epibionts were found in the fouling of ropes at the kelp farms of Primorye: 70 species of algae and 171 species of animals. The species richness of communities at the three kelp farms was 115, 118, and 114 species, respectively. Statistical significance of the differences between species lists (fiducial probability P = 0.95) was determined using a method based on a hyperbolic species-area model (Sukhanov, 1983). The results suggest that the three species lists represent a sample from the same general set. In the subsequent description of the dynamics of community, I used the results of the study of the fouling community from the rope substrates at the Kamenka kelp farm.

Seven species of macrophytes and 24 species of invertebrates were found in the Laminaria japonica community throughout the cultivation cycle. These are Punctaria plantaginea, Scytosiphon lomentaria, Laminaria japonica, and Costaria costata (Phaeophyta), Antithamnionella miharai, Ceramium japonicum, and Polysiphonia morrowii (Rhodophyta), Obelia longissima, and Bougainvillea ramosa (Hydrozoa), Metridium senile (Anthozoa), Gattyana sp., Harmothoe imbricata, Typosyllis pylchra occidentalis, Nereis pelagica, N. zonata, and Serpula vermicularis (Polychaeta), Ampithoe sp., A. eoa, Jassa marmorata, Pareurystheus gurjanovae, Pontogeneia kondakovi, Caprella sp., C. acanthogaster, C. cristibranchium and C. mutica (Amphipoda), Epheria turrita and Coryphella athadona (Gastropoda), Mytilus trossulus, Pododesmus macroshisma and Hiatella arctica (Bivalvia), Celleporella hyalina (Bryozoa). The absolute dominant and edificator of the community under study is L. japonica. Background-forming species of the epiphyton were the red algae A. miharai and P. morrowii the hydroid O. longissima, the amphipods J. marmorata and Caprella sp., and the nudibranch C. athadona.

The kelp Laminaria plays a leading role in the development of a community on the rope substrate. The present study enables us to consider this community as a consortium. As the kelp grows, its edificator properties change: the rhizoids accumulate detritus and provide a substrate and shelter to a variety of mobile animals. The thallus, stipe, and rhizoids by themselves become the substrate for epiphytic organisms. Respiratory activity and the amount of metabolites exuded into the environment vary with development stage of the macrophyte.

The first gastropod spawn masses on laminarian thalli appear in middle January at negative water temperature (up to -1,4°C). The mass reproduction begins in April at water temperature of up to 5°C and continues to the beginning of June.

Pioneer Stage of Succession of Fouling Community of Rope Substrate

After seeding, gametophyte culture ropes are placed in the sea in September-October (Krupnova, 1985). The first two to five months of exposure (November-February) correspond to the first development stage of the community on the ropes. The germination of gametophytes from the spores starts. At this period the kelp is not the edificator species. Along with the germination of Laminaria, the settlement of fouling organisms, whose larvae and spores are present in sufficient quantity in the plankton, occurs. Rope substrates are colonized by organisms from the fouling biotopes of the kelp farm. The fouling of ropes, at this period, was represented by the hydroid Obelia longissima community. Under favorable conditions, the hydroid O. longissima can form substantial biomasses, thus becoming a major space competitor of the kelp. This is the decisive period for the fate of the kelp harvest, which is expected in one and half to two years. After a month of exposure, hydroids were the dominant species and accounted for 82% of the total biomass, which has an average of 12.8 g/m. The subdominant was the nudibranch C. athadona for which hydroids are prey. The biomass of mollusk was 2.2 g/m (17.0%) and density 452.8 ind./m. During the observation period, predatory species (caprellids and nudibranchs) appreciably affected the structure of community. As hydroids are grazed, caprellids and mollusks are eliminated. Twenty-three species of plants and animals were recorded in the community at this period; most of them were common fouling organisms. Amphipods were dominant in species richness, representing 34.8% of the number of species.

First-year Growth Stage of Laminaria

A second stage in the development of community on rope substrates takes place during the 5th-8th months after placing the ropes in the sea (March-June). This period is characterized by a rapid growth of young sporophytes of Laminaria. Maximum Laminaria biomass was up to 2.5 kg/m, average value 730.8 g/m. The kelp had a voluminous rhizoid (Buyankina, 1981) which provides a habitat for a number of mobile animals; the bivalves Mytilus trossulus and Hiatella arctica were noted in the community; encrusting bryozoans Celleporella hyalina appeared on the rhizoids. The average biomass of epiphyton was 23.1 g/m. Forty-eight species were recorded in the community, with amphipods being dominant with respect to the number of species (27.1%). In general, this period is characterized by a negative correlation between epiphyte abundances and kelp biomass (r = -0.893, p < 0.05).

Stage of Degradation of the First-year Thallus

A third stage of the development of community on ropes occurred during the 9th-14th months of exposure of the substrates (July-December). At the beginning of this period, the maximum average annual surface water temperature was observed (to 18°C). Growth of Laminaria was delayed and sporophytes partly degraded, due to a summer rise in temperature of the water. At maximum water temperature, the average biomass of Laminaria on substrates decreased to 523.7 g/m. Hydroids (49.0 g/m) made the largest contribution to the biomass of epiphyton (55.6 g/m, on average). At this most unfavorable period for Laminaria, spirorbids, with a density of up to 334 ind./m, appeared in the epiphyton, In all, 73 species were recorded. New species continued to enter the community as detritus accumulated among the rhizoids. The community was dominated by polychaetes and amphipods (23.3 and 17.8%, respectively).

Second-year Growth Stage of Laminaria

This stage corresponded to the 15th-18th months of exposure (January-April). A vigorous second-year growth of the thallus occurred. At the end of the cultivation cycle (April, 18th month), Laminaria biomass was maximal. In the upper portion of the rope substrate, the macrophyte biomass was up to 20.4 kg/m, average thallus length 234 cm. Along with the increase in quantitative indices of macrophyte substrates, there was an increase in the biomass of epiphyton. The average biomass of epiphyton was 100.4 g/m. Before the harvest time, maximum abundances of bivalves were noted. Biomass of the mussel M. trossulus was 22.2 g/m and density 14.3 ind./m. The greatest changes in abundance were found for the spirorbid C. armoricana which appeared at the preceding stage. Spirorbids in mass colonized Laminaria thalli. Massive colonization by spirorbids made Laminaria unsuitable for use as food; their density on kelp thalli steadily increased, reaching 95'000 ind./m. Epiphyton exhibited maximum species richness at this period; 80 species were recorded; epiphytic algae were represented by 29 species. Amphipods (26.3%) and polychaetes (20.0%) were dominant on the basis of the number of species.

It is likely that the general course of development of community is explained by the physiological state of growing kelp. Most macrophytes exhibit a pronounced antibiotic activity (Wahl, 1989), which does not remain constant throughout their life cycle and changes with the seasons (Hornsey and Hide, 1976). In most macrophytes, maximum activity is observed during the spring when algae are devoid of epiphytes. In some cases, antibiotic activity changes with age. Maximum activity is found in young, actively growing plants, as well as in mature algae at transition to active growth (Sobot et al., 1980). The present study suggests that the development of a fouling community on substrates for the cultivation of L. japonica is dependent on the physiological state of the alga.

ACKNOWLEDGMENTS

This work was supported by the Russian Foundation for Basic Research, (project number 96-15-97957).

REFERENCES

Buyankina, S.K. 1981. Growth and Development of Laminaria japonica at Kelp Farms in Primorye. In: Promyslovye vodorosli i ikh ispol'zovanie (Commercial Algae and Their Applications), Moscow: Vsesoyuzn. Nauch. Issled. Inst. Ryb. Khoz. Okeanogr. pp. 35-39. (in Russian)

Hornsey, I.S. and Hide, D. 1976. The Production of Antimicrobial Compounds by British Marine Algae. III. Distribution of Antimicrobial Activity within the Algal Thallus, Br. Phycol. J. vol. 11, pp. 175-181.

Krupnova, T.N. 1985. Opyt kultivirovaniya laminarii yaponskoi po dvukhgodichnomu tsiklu v Primor'e (obzor) (Experimental Two-Year Cultivation of Laminaria japonica in Primorye: An Overview), Vladivostok: Tsentr. Proektn. Konstr. Buro Tekhn. Dalryby. 22 p. (in Russian)

Sobot, S., Span, A., and Maskovic, N. 1980. Antibiotska aktivnost nekih bentoskih alga u okolici Splita, Acta Adriat. vol. 21, no. 2, pp. 95-100. (in Poland with English summary)

Sukhanov, V.V. 1983. A Method for Determination of Statistically Significant Branches on a Dendrogram of the Similarity of Species Lists. In: Teoretiko-grafovye melody v biogeogrqficheskikh issledovaniyakh (Graph and Theoretical Methods in Biogeographic Investigations), Vladivostok: Dalnevost. Nauch. Tsentr Akad. Nauk SSSR. pp. 13-19. (in Russian)

Wahl, M. 1989. Marine Epibiosis. I. Fouling and Antifouling: Some Basic Aspects, Mar. Ecol. Prog. Ser. vol. 58, pp. 175-189.

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