The Ecology of Tijuana Estuary, California: An Estuarine Profile

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Water Depth fcmi Dry 1 3 5 7 9 1115 DfY 1 3 5 7 9 1115 ............ 3.6.1 Algae The obvrous plants of tntertrdal and subttdal areas are the macroalgae Vascular plants such as eelgrass (Zostera marrna) are absent, perhaps because the area of shallow water is too small or too dynamic for rooted plants to become established However, large populations of Enferomorpha sp and/or sea lettuce (Ulva sp, Ftgure 37) somet~mes develop on the channel bottoms and later float to the water surface (Rudn!cki 1986) Seasonal dtstributron patterns are highly variable, but their abundance is usually greatest In sprlng (Chapter 4) Figure 35. Comparison of feeding patterns for four species of birds that feed in the blocked channel of Tijuana Estuary. Foraging microhabitats (entire stippled area) were defined as the water depth where birds were observed feeding and the depth to which they probed the sediments; dense stippling indicates where species spent more than 805 of their time foraging; number in brackets is sample size (reprinted from Boland 1981 with author's permission). 3.6 ESTUARINE CHANNELS AND TlDAL CREEKS The channel habitats are important for a variety of organtsms including macroalgae, phytoplankton, invertebrates, ftshes, and birds (Figure 36) The Caiifornia least tern and other fish-eating species use deeper-water habitats, while shorebirds feed tn the intertidal zone at low tide Shorebtrd uses are d~scussed in the following section Channels are sublected to a wide range of envrronmental conditions Tidal flushing is greatest at the mouth and decreases with distance from the mouth, th~s general gradient In turn rnfluences water movement, salinity, temperature, nutrients, and d~ssolved gases Finer sediments are removed by hlgher current ~elOCitie~, so that substrates near the mouth have coarser sediments than in t~dal creeks Nutrtents brought into the estuary by tidal flush~ng are more readtly available to organrsms near the mouth Temperature salin~ty. and dissolved oxygen are less variable in areas of deepest water than In tidai creeks These environmental factors ~nfluence the species composttton, distributton, and populatfon dynamics of the channel organisms Phytoplankton are also vartable in species composit~on and density Dinoflagellates (e.g.. Gymnod~n~urn spp 1, diatoms, f~lamentous bluegreen algae (cyanophytes), and unidentified unicelis or "monads" are all present rn the water column (Ftgure 37, Fong 1986) Wh~le mast of these algae are typical planktonic species, the diatoms are all pennate forms with brlaterat symmetry and longitudtnal grooves that allow locomot~on on substrates Fong believes that most of these are resuspended from the sediments. The monads are so tiny ica 1-2 microns diameter) that tdent~fication IS challenging; they appear to belong to the Cyanophyta (P Fong, SDSU, pers comm.). Many of the phytoplankton species also occur In nearshore habttats, where their densities are lower During March-June blooms In the estuary, cell counts are higher than in marine waters by one to two orders of magnitude Both Rudnickt (1986) and Fong (1986) associate algal blooms with reduced lrdal flushing The air photo of March 1984 (F~gure 13) shows high biomass of macroalgae in tidal creeks and along the shores of the abandoned sewage lagoons Because the 1983 winter storm washed dune sands into the matn estuarine channel, tidal flushing became sluggrsh and algal btornass accumulated Likewise, algal growth was high during the nontidal period of 1984 Channel waters were green with phytoplankton dtirrng the summer (Chapter 4) During the 1985 monthly censuses of channel algae, Rudnlcki and Fong found the highest biomass of both macroalgae and phytoplankton in small t~dal creeks where current speeds were low 3.6.2 Benthie invertebrates Studies of invertebrates at Tijuana Estuary have included resource inventories and short-term or species-specrfrc tnvestigatrons, but most were conducted before the catastrophic disturbances d~scussed in Chapter 2. Data collected from precatastrophrc observations by a number of
Frgura 36 The etraracrel an& tidal ccsak hebitat8 ruppost an abundance of species tnclud~ng the marbled godw~t. wltkciu prabas @re%&dimant% for fsad, the tapsm@lt, whrctl attaches its eggs to macroalgao, the dramond turbot, whrcll feed% iian tlrU bentkt6 arpan(an?s, and gaper clams (Tresus nuffellrr), ghost shrtmp, and cammensal arrow potjtee, wh~ch live wlttltn the ua$imorrt% Mcinttre collectian, copyr~ght 1986 by Zedler snvu:g!lgitabf% (Byb~>(: lWY, Mcilwea I970 F~rrcl el rrracrofaunal comrnijnity IS very d~fferent frorn that rj$ I 9r* 1 Srr:t%I~ Iq4:)p-4 Pcrters~n l HP5 Inlernlattutlal descr~bed in ltre 1970's B~rd~r Walar Carnrrtrssrorl 1$3i"ii, Cf Dexic:r SDSlJ wrryrubl diitcs ;tt?tJ Wtrct~ i~t~d WVundt>!li@Yr wnpilbl srs r:cutrtbrncld to dttpiri the tt!vertosbr;ate ce~inmurtlty Before 1980 the benthic comrnunlly was uf?t.i~?r RloW R L R ~ ~ E ? f:t>ll
Page 1 and 2: June 1986 I THE ECOLOGY OF TIJUANA
Page 3 and 4: The findings in this report are not
Page 5 and 6: CONVERSION TABLE Metric to U.S. Cus
Page 7 and 8: Page 4.5 Energy Flow ..............
Page 9 and 10: Number Page The channel fish cornrn
Page 11 and 12: ACKNOWLEDGMENTS The California Sea
Page 13 and 14: Figure 1. Lacatlcrn of 71juana Estu
Page 15 and 16: Figure 3. Map6 of Tijuana Estuary s
Page 17 and 18: FI(I(uPc$ 4. Wei&rahOt@ patt@rns of
Page 19 and 20: also limitrng Hot, dry desert winds
Page 21 and 22: 2.3 LAND USE HlSPQWV Through exami!
Page 23 and 24: The nearby bridge remained, and ext
Page 25 and 26: flushing until mid-December 1984. E
Page 27 and 28: with seawater. Even in years with s
Page 29 and 30: flats ~n winter but not in midsumme
Page 31 and 32: Each "island" of higher topography
Page 33 and 34: The vegetation and soils of the upp
Page 35 and 36: populations (Massey 1979) The brrds
Page 37 and 38: c~n~entrations of insects, especial
Page 39 and 40: Frgufe 29. The Ifght-footed clapper
Page 41 and 42: Figure 30. During winter (above) th
Page 43 and 44: anlmal footprints, In the hardpan f
Page 45: Tijuana Estuary salt marsh Such exp
Page 49 and 50: ^_ _I __"___I _-a_. -- fable 7. Inv
Page 51 and 52: Pre- 1980 (excluding Hosrner Rehse
Page 53 and 54: Table 8. Average density (number/m2
Page 55 and 56: changes in envlronment has not been
Page 57 and 58: was dominated by goby species, Cali
Page 59 and 60: compared the ,chthyoplankton commun
Page 61 and 62: Figure 43, Birds of the intertidal
Page 63 and 64: -" and that the community was compo
Page 65 and 66: Willet (1 73) i - Water Depth (cm)
Page 67 and 68: Table 14. Early information on dune
Page 69 and 70: Figure 48. Birds that nest on the s
Page 71 and 72: CHAPTER 4 ECOSYSTEM FldNCTlONlNG St
Page 73 and 74: were no? irght-saturated untri expo
Page 75 and 76: Table 17. Conceptual model of chann
Page 77 and 78: Table 19. Net aboveground productiv
Page 79 and 80: _I___ I__-~--- 4.4.1 Nitragen Fluxe
Page 81 and 82: i i t 1 1 I Table 22. Standing crop
Page 83 and 84: calculated from chlorophyll a measu
Page 85 and 86: Dissolved Organic Biomass Carbon De
Page 87 and 88: CHAPTER 5 THE ROLE OF DISTURBANCES
Page 89 and 90: Table 25. Changes in elevation in t
Page 91 and 92: Table 26. Change in pickleweed cano
Page 93 and 94: Table 27. Occurrence (in circular 0
Page 95 and 96: perennials can survive long periods
Page 97 and 98:
An experiment was designed to deter
Page 99 and 100:
CHAPTER 6 MANAGEMENT CONSIDERATIONS
Page 101 and 102:
Closely associated with the researc
Page 103 and 104:
c. Dredging at Tijuana Estuary will
Page 105 and 106:
Table 30. Predicted impacts of redu
Page 107 and 108:
footed clapper rails; the picklewee
Page 109 and 110:
overwashas, and slabiiizatran rs rl
Page 112 and 113:
REFERENCES Allen, L.G. 1980. Struct
Page 114 and 115:
Minsky, D. 1984. California least t
Page 116:
30272 -101 REPORT WUMENTATION 1. RE
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The Ecology of Tijuana Estuary, California: An Estuarine Profile

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