Zostera Marina and Ruppia Maritima to the 8Lack8rant, Branta Berniclanigricans, San Ignacio Lagoon, Baja California, Mexico
Total Page：16
File Type：pdf, Size：1020Kb
THE RELATIONSHIP OF TWO SEAGRASSES: ZOSTERA MARINA AND RUPPIA MARITIMA TO THE 8LACK8RANT, BRANTA BERNICLANIGRICANS, SAN IGNACIO LAGOON, BAJA CALIFORNIA, MEXICO by DAVID KUME WARD A THESIS Presented to the Department of Biology and the Graduate School of the University of Oregon in partial fulfillment of the requirements for the degree of Master of Science August 19~3 ii APPROVED: ~a...&S?~ Paul P. Rudy , iii An Abstract of the Thesis of David Hume Ward for the degree of Master of Science in the Depart~ent of Biology to be taken .!\ugust 1983 Title: THE RELATIONSHIP OF TWO SEAGRASSES: ZOSTERA MARINA AND RUPPIA MARITIMA TO THE BLACK 3RANT, 3~ANTA 3ERNICLA NIGRICANS, SAN IGNACIO LAGOON, BAJA CALIFORNIA, MEXICO APproved:~12& b "7 Paul P. Rudy San Ignacio Lagoon, Baja California, is a major winter- ing grounds for Black Brant, Branta bernicla niqricans, along the Pacific coast of North America. Two sources of food for Brant, Zostera marina and Ruopia maritima, occur in the lagoon. During December 1982 to April 1983 studies were made on the i~tertidal standing crop and production of Zostera and on the feeding behavior of the Brant. 8i- monthly Zoster~ standing crop and production values decreas- ed throughout the period. This seemed to be controlled by insolation. Survey data indicated that Brant favored Ruppia to Zostera as forage. The reasons for this selection appear to be nutritive value and availability of Rwppia. Protein analyses revealed that Ruppia is as good as or an even better source of protein for the birds than Zostera. Ruppia grows higher in the intertidal than Zostera and iv hence is more frequently exposed and available as a food source. v VITA NAME OF AUTHOR: David Hume Ward PLACE OF BIRTH: Elmira, New York DATE OF BIRTH: 1~ April 1952 UNDERGRADUATE AND GRADUATE SCHOOLS ATTENDED Hartwick College University of Oregon DEGREES AWARDED Bachelor ofArts, 1974, Hartwick College AREAS OF SPECIAL INTEREST: Ornithology S.C.U.B.A. Research Aquaculture PROFESSIONAL EXPERIENCE Museum Preparations AWARDS AND HONORS Sigma Xi Grant 1982-1983 National Merit Scholarship Fund vi ACK NDWLED GEr-l ENT To thosd for wham I have nat taken time to thank, I now express my gratitude for the encouragement. It was Lu- anne Smith who pushed me in the right direction, and my ad- visor Paul Rudy who allowed me to pursue this idea. The guidance was provided by Ran Phillips and the friends at D.I.M.B.. Funds were partly provided by a grant from Sigma Xi. Special appreciation goes to my father, Bill Ward, who helped support and endure the living in Baja, Mexico. To my technical assistances, Lee Tibbitts and Janet Essley, who shared this winter adventure, I owe a great deal, and would like to share this quote by Lewis Thomas from IILives of a Cell": "I don't know of any other activity in which the people engaged in it are so caught up, so total ly preoccupied...... It looks like a lonely ac tivity but it is as much the apposite of lonely as human behavior can be. There is nothing to touch the spectacle. In the midst of what seems a collective derangement of minds in total dis order, there emerges suddenly with the purity of a slow phrase of music, a single new piece of truth about nature. 1I v-ii TABLE OF CONTENTS -Paoe INTRODUCTION • • • • • • • .. .. ·.. • • • • • • 1 Study Area • • • • • • • • • • • • • • • • • 6 MATERIAL AND METHODS • •• ... .." , .. • • • • · .. - . 9 Exclusion Cages ••• • • •• • • • • ·.. 9 Samples and Analysis • • • •• • • • • • • • 9 Brant Dynamics •••• • ••• • • • • • • • 10 Statistical Procedures • • • • • • • • •• • 14 RESULTS •• • • • • • • • • • • • • • •• • • • • 17 17 Exclusion Cages • • • • • • • • ·- ... .. • • Seagrass Dynamics • • • • • • • ·. ..... .. 17 Brant Dynamics • • • • • • • • • •• • • • • 35 CONCLUS ION • • •• • • • • • • • • • • • • • • • 41 Zostera Dynamics • • • • • • • • • • • • • • 41 Brant Dynamics • • • • • • • • • • • • • • • 45 APPEND IX • •• •• •• • • • • • • • • • • • • • 50 Tables and Figures • • • • • • • • • • • • • 50 REFERENCES • • • • • • • •• • • • • ••• • • 56 viii LIST OF TASL:::S Ta ']le -Pace 1. DifFerences in standin~ crODletween r"1razed and un;,razed q!Jadrats ••••• 20 ~ ':::. Conparison of mean standin] croD, shoot density, leaf length and leaf width at three intertidal hei]hts ••••••• •• 21 3. ~eans of oroduction, new leaf energence, leaves per shoot and leaf attachment time of Zostera from sites 2 and 3 •• •• 29 4. DailV in situ net oroduction of Zostera the ~ans-of sites 2 and 3 .. .. · . 30 5. Percent protein content of Zostera and Ruppia ••••••••••••• ••••• r:L. • Zostera consunption by Brant between 14 Feb. to 14 ~arch, 1383, on the tide-flats at Punta Piedra ••••••••• •• •• 36 Ash content of 10, O.1m 2 dry weight samples ••• . ...... •• • • 51 A2. Comparison of holes in Zostera shoots as a measure of production with a 2nm punch and a sewinG needle •••••• · . 52 A3. Ash content of 20, 10cm se1ments of Zoste~a leaves; as used as a conversion factor for length to weight ••••••• 53 ALf • Concentrat:ons of prote:n as expressed in ootical densitv of Zostera leaves at three sites and Ruppia leaves at one site ••••• .... .... 54 • ix LIST OF FIGURES Figure -Paoe 1. San Ignacio Lagoon, Baja California, Mexico ••••••• ••••••••• • •• 7 2. Three intertidal collecting sites at Punta Piedra tide-flat •••••• • • • 8 3. Comparison of bimonthly shoat lengths of Zostera from sites 1, 2, and 3 • • • 22 4. Linear regression of bimonthly mean leaf widths of Zostera from sites 1, 2, and 3 ••••••••••• ••• 23 5. Comparison of mean bimonthlv standing crop of Zostera from sites 1, 2, and 3· •• e- • •.•. ••••••••••• • • 24 Linear regression of bimonthly standing crop and leaf length of Zostera at three sites • ~ ••• • •• • 25 7. Linear regression of bimonthly in situ ne~ Zostera production from combined means of sites 2 and 3 • • •• 31 8. Seasonal changes in plastochrone interval of Zostera compared with insolation and temperature • • • • •• • 32 9. Four Brant censuses and grazing areas • • 38 A1. Linear regression for a protein curve. •• 55 1 INTRODUCTION Harbors, estuaries and nearshore shallow coastal waters of the world comprise only 1% of the surface area of the world's oceans. Yet, these nearshore areas are inhabitated by tke most highly productive ecosystems in the world (Phil lips, 1978). These ecosystems are dominated by marine plants, of which. the seagrasses are highly important. They are marine angiosperms which grow in shallow coastal waters of the tropical and temperate zones. The various genera of seagrasses are not closely related to each other and in fact are not true grasses (Family Poaceae). Rather, they are more closely related to the Lily family (Family Li1iaceae) (Dawes, 1981). Seagrasses perform a variety of biological and ecologi cal functions in coastal environments. These are summarized by Wood et a1. (1969): 1) Seagrasses have a very high primary production rate (McRoy and McMillan, 1977; Dawes ~ ~., 1979). Production 2 rates of 500-1000 gC/m /yr. can be typical and even higher • 2 rates may be reached in some areas. Approximately 50% of the carbon lost is in the form of dissolved organic carbon (Dawes, 1981). 2) The leaves support large numbers of epiphytic organ isms, often with a biomass approaching that of the plants themselves. 3) Though very few o2ganisms graze directly on sea grasses, many graze on associated epiphytes. Most of the food chain is based on detrital pathways. 4) Organic material in the detritus and decaying roots aid in maintaining an active sulfur cycle. 5) Essentially the grasses serve as effective sedi ment traps. The roots and rhyzomes bind the sediments in place, and with the protection of the leaves, inhibit ero sion. The dense leaves retard currents and increase sedi mentation on organic material around the plants. The sea grasses provide a preserve for the microbial flora of the sediment and sediment-water interface. 6) Seagrass communities provide an important habitat and shelter for many animals. Kikuchi (1974) found a signi ficant decrease in the numbers of decapods and juvenile and young-adult stages of commercial fish as a result of a de crease in Zostera marina production. 7) Seagrasses absorb nutrients through their leaves and roots. Nitrogen and phosphorous can be returned to the water via leaching and degradation of the leaves. 3 There are 49 species of seagrasses classified into 3 families and 13 genera. The family Potamogetonaeceae con tains 9 genera and 34 species; the family Hydrocharitaceae contains 3 genera and 11 species (Phillips, 1978); and the family Ruppiaeceae contains 1 genus and 4 species (Hutchin son, 1934, 1959). In the family Potamogetonaeceae the genus Zostera in habits th~ temperate waters of the Northern Hemisphere. Two species of Zostera are found along the Pacific coast of North America of which Zostera marina L. is the most dominant and widespread. The genus Ru~ has had a history of confused taxonomy at ~oth the specific and familial level (Jacobs and Brock, 1982). Even in Europe where the taxonomy is more understood (Verhoevan, 1979), recent evidence suggests that new taxa should be made (Van Viersson ~ ~., 1981). At present in North America there is only one marine species of the genus Ruppia, e.g. Ruppia maritima L•• The distribution of Ruppia maritima is cosmopolitan. Along the Pacific coast it is found from the Bering Sea to Mexico (Fernald, 1950). As stated earlier one of the most important functions of seagrass communities is their high production rate, with a range of 0.2 - 7.0 gC/m 2/day (McRoy and McMillan, 1977), however, most organic material produced by the seagrasses is utilized through detrital food chains (Fry et ai., 1982; McConnaughey and McRoy, 1979). Very few organisms are able 4 to use seagrass tissus directly (Kikuchi, 1966; Kristensen, 1972). Along the Pacific coast of North America the animals that do are predominately herbivorous birds (Cottam ~, aI, 1944; Martin g1 ~1; 1951), invertebrates (McConnaughey and McRoy, 1979; Lawrence, 1975), green sea turtles (Felger et al. 1976) and Seri Indians (Felger and Moser, 1973). One of the major herbivores of seag~asses is the Pacific Black Brant, Branta bernicla nigricans,(Lawrence, 1846), a relatively small goose.