Table Of ContentGreatBasin Naturalist55(2),© 1995,pp. 164-168
SEASONAL NUTRIENT CYCLING IN POTAMOGETONPECTINATUS
OF THE LOWER PROVO RIVER
C. Mel Lytle' and Bruce N. Sniitlii-2
—
Abstiuct. Acommon submersedaquaticplantofGreat Basinwetlandandriverinesystems,Potamogetonpectina-
tiis L. (sagopondweed) isakeywaterfowl food. Nutritionalqualitiesofsubmersedaquatics intheGreat Basinarelittle
understood. The puipose ofthis study was to determine the seasonal element cycling and nutritional qualities ofP.
pcctiiialus drupelet, leaf and root tissues from thelower Provo River. Leaftissueprotein was27% (dryweight) inJuly,
hutdeclinedto 15%byDecember Diiipeletproteincontentwas9%inJulyand6.5%inOctober. Lignocelluloseinleaf
tissuewas lowestinJulyat34%andincreasedastheseasonprogressed. Percentfatwashighestin leaftissueat 12%in
|ulv Sugars were highest in P pectinatus leaftissues in December and July. Calcium and magnesium concentrations
increasedinPpectinatustissuesovertheentireseason. Leaftissuezincwas329ppm(diyweight)inOctober Leafiron
concentration was highest in Septemberat 1184 ppm, while roottissue ironwas 7166ppm. Manganese contentin leaf
tissuepeaked inOctoberat4990ppm. Copperconcentrations inleavesandrootswerevariable. Highproteininleaftis-
suewouldbenefitlocalnestingandbroodingwaterfowlpopulationsthatfeedonthisaquatic.Tracemetalconcentrations
in leafand root tissues, fi-om possible anthropogenic activities, appear veiy high during fall migratoiy months. Metal
bioaccumulation bythis species in otherGreat Basinwetlands andpossible metal toxicityinwaterfowl warrant ftuther
study.
Keywords:sagopondweed. Potamogetonpectinatus,nutritionalqualities, traceelementcycling, metalbioaccumulation,
waterfowl.
A common submersed aquatic plant of the condition and nutritional requirements are
Great Basin, Potamogeton pectinatus is a key based on studies from other areas of North
priman' producer in fresh and sahne wetlands America. Yet, energy and sustenance required
(Kantrud 1990). Waterfowl feed on all plant by waterfowl species that frecjuent the Great
parts including drupelet, leaf, and root tissues Basin are largely provided by resident aquatic
(Anderson and Ohmart 1988, Korschgen et al. plants. Of these, P. pectinatus, Ruppia mariti-
1988). Sherwood (1960) noted that whisding ma L. (widgeon grass), Scirpus mahtimus L.
swans {Olorcolumhianus) fed heavily on tubers (alkali bulrush), Scirpus pungens L. (Olney
and drupelets duringfall migration in the Bear three-square), Scirpus acutus L. (hardstem
River Migratory Bird Refuge and O—gden Bay bulrush), and Zannichellia palustris L. (horned
Refuge. Other waterfowl species Canada pondweed) are common plant species man-
geese {Branta canadensis), mallards {Anas platy- aged in national refuges and waterfowl man-
rhynchos), pintails {Anas acuta), gadwalls {Anas agement areas. Potamogeton pectinatus is con-
strepera), canvasbacks {Aytha—vallisneria), and sidered the most important of these species
redheads {Aytha americana) also fed on P. for diving and dabbling ducks (Kadlec and
pectinatus leafand root tissues. Localized inter- Smith 1989). The purpose ofthis study was to
mountain trumpeter swan {Cygnus buccinator) determine the seasonal element concentra-
populations are also largely dependenton sub- tions and nutritional qualities of P. pectinatus
mersed aquatic plants as food (Anderson et al. from a local Great Basin riverdrainage.
1986, Henson and Cooper 1993).
Little is known concerningnutrient dynam- Methods
ics and seasonal element cycling ofP. pectina-
tus from Great Basin wetlands (Kadlec and Plant harvests were conducted monthly
Smith 1989). Consequently, how this aquatic from three locations within the lower Provo
species may affectwaterfowl nutrition ispoorly River drainage from July 1991 to December
understood. Mostassumptions concerningbody 1991: (1)justbelow DeerCreekdam (40°24'N,
'DepartmentofBotanyandBangeScience.401WIDE,BrinliariiVounKIiii\ersit>.Provo.UT84602.
^Authortowhomcorrespondenceshouldbeaddressed.
164
1995] Seasonal NutrientCycling in P. pectinatus 165
Table 1. A range ofmeasured water column and sedi-
mentcharacteristics, pH, andelectrical conducti\'it\' (EC)
fromthelowerProvoRiverdrainage.
Water
Claritv
166 Great Basin Naturalist [Volume 55
dry matter content observed in October. Percent nitrogen (N) and phosphorus (P) in
Throughout the season, P. pectinatus element leaftissue reached peak concentrations in July
and forage composition varied with growth but were significantly lower by December (F
stage. Significant variation in leaf tissue pro- = 23.37; d.f = 4,14; P < .001) (F = 79.30; d.f
tein was found (F = 21.69; d.f = 4,14; P < = 4,14; P < .001; Tible 4). Veniiaaketal. (1983)
.001) between July, September, October, and stated that P. pectinatus played an important
December (Table 3). Drupelet protein content role in P cycling in aquatic systems. Cultured
was higher in July than in October. In all P. pectinatus grown in water relatively high in
months sampled, leaftissue piotein was high- phosphate (PO4-P) (0.3 ppm) bioaccumidated
er than drupelet protein. Percent protein in p32 jq 4738 times the amount found in the
leaftissue was higher than values reported in water column. Nitrogen and P content in P.
other studies (Linn et al. 1975, Kantrud 1990). pectinatus can be well above that required for
Acid detergent fiber (ADF) analysis revealed plant growth; this would indicate luxuiy con-
that leaf tissue was lowest in lignocellulose sumption ofthese elements (Jupp and Spencer
(fiber) in July, but significant differences (F = 1977, Ho 1979, Madsen 1986). Significant
3.03; d.f = 4,14; P = .07) in fiber content concentrations ofcalcium (Ca) and magnesium
were not observed as the year progressed. (Mg) accumulated (F = 29.12; d.f = 4,14; P <
Linn et al. (1975) found P. pectinatus leaffiber .001) (F = 278.71; d.f = 4,14; P < .001) in
content of 33% that is similar to values leaf tissue between Jul\' and December. This
obsei-ved in this study. Increased fiber content may indicate abiotic deposition, though no vis-
would decrease the overall forage quality of ible encrustation on exterior leafor stem sur-
=
leaftissue. Significant variation did exist (F faces was obsei-ved. Hutchinson (1975) report-
177.40; d.f = 4,14; P < .001) in leaftissue fat ed that P. pectinatus leaves were higher in Ca,
content and was highest in July. Total non- Fe, K, Mg, Na, and several micronutrients than
structural carbohydrates (sugars) in leaftissues other aquatic plants. Yet, no mention of time
were highest in December and differed from sampled was given for these mineral concen-
all other months (F = 42.19; d.f = 4,14; P < trations. Therefore, no knowledge of seasonal
.001). By October, drupelet fat and sugar con- accumulation was determined. Potassium (K)
tent were both higher than values found in content was highest in September and differed
July. significantly from percent K content in July (F
Table3. Meanpiotein, fiber, fat, and sugarcontentin P.pectinatus drupeletandleaftissueoverfi\'e months. Forage
qualityconstituentsexpressedas%diyweight±S.E.,n > 3. Means sharingthesameletterarenotsignificantlydiffer-
ent(P < .05).
Monti
1
1995] Seasonal Nutrient Cycling in P. pectinatus 167
Table 5. Mean traceelementconcentration in P. pectinatus leaftissue overfive months. Elementcontent expressed
asppnicli"yweight±S.E.,n > 3. Meanssharingthesameletterarenotsignificantlydifferent(P < .05).
Month Zn Mn Cu
July
168 Cheat Basin Natur.\list [Volume55
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