80

REPORTS:

An inventory ofmeroplankton associated with spicatum, focusing on ephemerella, in Otsego Lake, summer 1997

Mary Miner·

INTRODUCTION

Myriophyllum spicatum, commonly known as Eurasion Watermilfoil, was first documented in Otsego Lake in 1986 (Dayton and Smith, 1986). It has since become a nuisance to lakeside residents, in places forming thick mats at the surface which potentially hinder boat travel and decrease property value. With a photosynthetic rate two to six times that of native (Anon, 1986), and an earlier annual period of growth (Hutchinson, 1975), M spicatum reduces native plants' chance to compete for light and space.

The spread of M spicatum was closely monitored after its discovery. Subsequent growth and mapping of its distribution were recorded in 1987. At this time, clones of milfoil were found only in the northern part ofthe Lake (Merrifield and Harman, 1988). By 1988 it wasnoted that M spicatum had inhabited all substrates suitable for it's growth within the Lake, including the south end (Stalter, 1989). In the summer of 1990, the percent cover of M spicatum at four sites showed that it was a dominant species throughout the littoral zone (Sanders, 1990).

It has been observed that M spicatum has not created as large a problem in Otsego as it has in many other lakes. It has been proposed that this is due to the presence ofAcentria ephemerella, a lepidopteran which, in its larval stage, feeds on the meristematic region of milfoil (Harman, 1998). The larvae's feeding habits cause the plants to grow laterally rather than vertically. The result is shorter clones of M spicatum which do not reach the surface of the water. This years study focuses on the meroplankton found to inhabit M spicatum beds, with emphasis placed on evaluating the densities ofA. ephemerella.

Meroplankton (defined as the macroinvertebrate community living in direct association with macrophyte beds) were surveyed at four sites on Otsego Lake. The selected sites were dominated by milfoil. Special attention was paid to Acentria to investigate whether or not it may be controlling the growth of M spicatum.

• F.H.V. Mecklenburg Conservation Fellow, summer 1997. Present affiliation: Cooperstown Central High School. 81

MATERIALS AND METHODS

On July 11,24, and August 7, 1997, four sites, accessed by boat, were chosen for the purpose of finding representative areas from which to sample M spicatum. The sites were located at the north and south ends of the Lake, Rat Cove and Hyde Bay (Figure 1). At each location, M spicatum was collected by hand and placed in 5 gallon buckets. The milfoil was covered with water and allowed to sit for a period of 2 to 4 days so that the invertebrates would come loose from the plants. At the end of this period, each bucket was sorted through by hand and the meroplankton was extracted. The invertebrates were placed in 70% ethanol for later identification. The milfoil was saved to be dried and weighed in order to attempt to normalize densities.

The meroplankton were identified (Merritt, 1996), (Pennak, 1989) and sorted according to site, date and taxon. Their numbers and weights were recorded in order to find the biomass per unit of milfoil (dry weight) at each site.

RESULTS AND DISCUSSION

Table 1 shows the taxa encountered during this study. Tables 2-13 show the biomass of species found per biomass of milfoil for each site on all three dates. Differing amounts of milfoil were collected at each site. Therefore, grams of species per kilogram of milfoil was determined in order to present the data semi-quantitatively. Information about Hyde Bay is synthesized in Tables 2-4; the north site in 5-7; Rat Cove in 8-10; and the south site in 11-13 (See Figure 1 for site locations).

Milfoil was found to be dense at the site on the North end of the Lake, Hyde Bay, and in Rat Cove. Hyde bay was the only site having significant representatives of other macrophyte species. At the South end of the Lake, milfoil clones were significantly less dense than in the other three sampling sites.

Several observations of milfoil were made upon each collecting date. The beds ofM spicatum were noticeably thicker later in the season. It was also observed that the clones of milfoil did not create large mats at the surface at any sites. In Hyde Bay, Rat Cove, and the south site, the milfoil did not reach the surface, and rarely did so at the north site.

On July 11, Acentria was found only in Rat Cove and the north site. On July 24, it was found in the two previous sites as well as in the south site. During the second sampling, Acentria were discovered to be much more numerous. The third sampling found Acentria equally as numerous as in the second sampling. Rat Cove and the north site were the only sites in which Acentria was found on all three dates.

The explanation for the low numbers ofAcentria on the first collecting date was that the species were at the end oftheir first 1997 generation. The second and third collecting dates 82

Otsego Lake

Rat Cove Site

o 1 f

South Site r.USOUF.II/\NN/\ nIvr 1\

Figure 1: Sites of M. spicatum collection on July 11, July 24, and August 7, 1997.

*-Site location 83

All Sites, Summer 1997 TAXA July 11 July 24 August 7 Platyhelminthes

Turbellaria ~ Tricladida Planariidae ...... Annelida Hirudinea Pharyngobdellida Erpobdellidae .. .. Rhynchobdellida Glossiphoniidae Helobdelfa stagnalis .. .. Oligochaeta Haplotaxida Naididae ...... Mollusca Gastropoda Basommatrophora Planorbidae Gyraulus parvus ...... Physidae Physa integra ...... Mesogastropoda Hydrobiidae Amnicola limosa ...... Arthropoda Arachnida Acariformes ...... Crustacea Amphipoda Talitridae Hyalelfa azteca ...... Isopoda Asellidae Caecidota .. Insecta Ephemeroptera Caenidae Caenis ......

TABLE 1: Taxa ofall sites, summer 1997 84

TAXA July 11 July 24 August 7 Odonata (Anisoptera) Libellulidae * Odonata ( Zygoptera) Coenagrionidae Coenagrion or Enallagma * * * Hemiptera Mesoveliidae Mesovelia * Nepticulidae * * * Pyralidae Acentria * * * Trichoptera Leptoceridae Mystacides * Oecetis * * * Hydroptilidae * Agraylea * Orthotrichia * * * Coleoptera Curculionidae * * * Diptera * Ceratapogonidae * Chironomidae * * * Empididae *

TABLE 1 (continued): Taxa of all sites, summer 1997 85

Otsego Lake Hyde Bay-July 11, 1997 TAXA Number In grams g/ko milfoil IPlatyhelmInthes Turbellaria Tricladlda Planariidae 7 0.0094 0.0001 Mollusca Gastropoda Basommatrophora Planorbidae Gyraulus parvus 7 0.0237 0.0003 Mesogastropoda Hydrobiidae Amnicola limosa 4 0.0375 0.0005 Arthropoda Arachnida Acariformes 5 0.0020 0.00003 Crustacea Amphipoda Talitridae Hya/ella azteca 9 0.0056 0.0001 Insecta Ephemeroptera Caenidae Caenis 2 0.0028 0.00004 Diptera Chironomidae 7 0.0074 0.0001

TABLE 2: Taxa of Otsego Lake Hyde Bay, July 11, 1997 86

Otsego Lake Hyde Bay-July 24, 1997 TAXA Number In grams g\kg milfoil IPlatyhelminthes Turbellaria Tricladida Planariidae 176 0.1989 2.5235 Annelida . Oligochaeta Haplotaxida Naididae 7 0.0006 0.0076 Mollusca Gastropoda Basommatrophora Planorbidae Gyraulus parvus 38 0.0653 0.8285 Physidae Physa integra 1 0.0024 0.0304 Mesogastropoda Hydrobiidae Amnicola limosa 18 0.1844 2.3395 Arthropoda Crustacea Amphipoda Talitridae Hyalella azteca 7 0.0019 0.0241 Insecta Ephemeroptera Caenidae Caenis 1 0.0017 0.0216 Trichoptera Leptoceridae Oecetis 1 0.0040 0.0507 Diptera Chironomidae 6 0.0010 0.0127

TABLE 3: Taxa of Otsego Lake Hyde Bay, July 24,1997 87

-- Otsego Lake Hyde Bay-August 7, 1997 TAXA Number In grams g/kg milfoil If-'Iatyhelmlnthes Turbellaria ~ Tricladida Planariidae 130 0.1026 0.0006 Annelida Oligochaeta Haplotaxida Naididae 2 <.0001 <.0001 Mollusca Gastropoda Basommatrophora Planorbidae Gyraulus parvus 73 0.1330 0.0008 Mesogastropoda Hydrobiidae Amnicola limosa 13 0.0289 0.0002 Arthropoda Arachnida Acariformes 1 0.0008 0.000005 Crustacea Amphipoda Talitridae Hya/ella azteca 7 0.0024 0.00001 Insecta Lepidoptera Pyralidae Acentria 1 0.0159 0.0001 Diptera Chironomidae 12 0.013 0.0001

TABLE 4: Taxa of Otsego Lake Hyde Bay, August 7, 1997 88

Otsego Lake North-July 11, 1997 TAXA Number In grams klkg milfoil Platyhelminthes Turbellaria Tricladida Planariidae 17 0.0272 0.1967 Annelida Hirudinea Rhynchobdellida Glossiphoniidae Helobdella stagnalis 2 0.0135 0.0976 Oligochaeta Haplotaxida Naididae 3 <.0001 <.0001 Mollusca Gastropoda Basommatrophora Planorbidae Gyraulus parvus 4 0.0079 0.0571 Mesogastropoda Hydrobiidae Amnicola limosa 1 0.0106 0.0767 Arthropoda Arachnida Acariformes 1 0.0004 0.0029 Crustacea Amphipoda Talitridae Hyalella azteca 11 0.0093 0.0673 Insecta Hemiptera Mesoveliidae Mesovelia 1 0.0007 0.0051 Lepidoptera Nepticulidae 4 0.0097 0.0702 Pyralidae Acentria 1 0.0003 0.0022 Trichoptera Leptoceridae Mystacides 1 0.0083 0.0600 Oecetis 1 0.0012 0.0087 Hydroptilidae Orthotrichia 8 0.0052 0.0376 Diptera Chironomidae 10 0.0024 0.0174

TABLE 5: Taxa of Otsego Lake North, July 11, 1997 89

-- Otsego Lake North-July 24, 1997 TAXA Number In grams g/kg milfoil _... PlalYflelminthes Turbellaria Tricladida Planariidae 223 0.2894 1.1870 Annelida Hirudinea Pharyngobdellida Erpobdellidae 1 0.0007 0.0029 Rhynchobdellida Glossiphoniidae He/obdella stagnalis 1 0.0195 0.0800 Oligochaeta Haplotaxida Naididae 4 0.0004 0.0016 Mollusca Gastropoda Basommartrophora Planorbidae Gyraulus parvus 31 0.0691 0.2834 Physidae Physa integra 16 0.0490 0.2010 Mesogastropoda Hydrobiidae Amnico/a limosa 13 0.1783 0.7313 Arthropoda Arachnida Acariformes 6 0.0025 0.0103 Crustacea Amphipoda Talitridae Hyalel/a azteca 34 0.0178 0.0730 Insecta Ephemeroptera Caenidae Caenis 2 0.0102 0.0418

TABLE 6: Taxa of Otsego Lake North, July 24, 1997 90

TAXA Number In grams g/kg milfoil Odonata (ZygopferaJ Coenagrionidae Coenagrion or Enallagma 1 0.178 0.7301 Lepidoptera Nepticulidae 2 0.0012 0.0049 Pyralidae Acentria 9 0.0362 0.1485 Diptera Chironomidae 10 0.0045 0.0185

TABLE 6 (continued): Taxa of Otsego Lake North, July 24, 1997 91

Otsego Lake North-August 7, 1997 TAXA Number In grams g/kg milfoil II-'Iatyhelmlnthes Turbellaria Tricladlda Planariidae 181 0.1743 0.0006 Annelida Oligochaeta Haplotaxida Naididae 19 0.0012 0.000004 Mollusca Gastropoda Basommatrophora Planorbidae Gyraulus parvus 101 0.1924 0.0007 Physidae Physa integra 2 0.0120 0.00004 Mesogastropoda Hydrobiidae Amnicola limosa 1 0.0013 0.000005 Arthropoda Arachnida Acariformes 4 0.0033 0.00001 Crustacea Amphipoda Talitridae Hyalella azteca 5 0.0035 0.00001 Insecta Ephemeroptera Caenidae Caenis 1 0.0029 0.00001

TABLE 7: Taxa of Otsego Lake North, August 7,1997 92

TAXA Number In grams g/kg milfoil Odonata ( Zygoptera) Coenagrionidae Coenagrion or Enallagma 1 0.0002 0.000001 Lepidoptera Nepticulidae 1 0.0002 0.000001 Pyralidae Acentria 4 0.0474 0.0002 Trichoptera Leptoceridae Oecetis 4 0.0094 0.00003 Hydroptilidae Orthotrichia 1 0.0001 0.0000003 Coleoptera Curculionidae 3 0.0044 0.00002 Diptera Chironomidae 18 0.0061 0.00002

TABLE 7 (continued): Taxa of Otsego Lake North, August 7,1997 93

Otsego Lake Rat Cove-July 11, 1997 TAXA Number In grams g/kg milfoil II-'Iatyhelmlnthes Turbellaria Tricladida Pfanariidae 13 0.0194 0.1820 Annelida Hirudinea Rhynchobdellida Glossiphoniidae Helobdella stagnalis 1 0.0022 0.0206 Mollusca Gastropoda Basommatophora Planorbidae Gyraulus parvus 2 0.0064 0.0601 Physidae Physa integra 1 0.0040 0.0375 Mesogastropoda Hydrobiidae Amnicola limosa 4 0.0292 0.2740 Arthropoda Crustacea Amphipoda Talitridae Hyalella azteca 2 0.0034 0.0319 Insecta Ephemeroptera Caenidae Caenis 4 0.0132 0.1239 Odonata (Zygoptera) Coenagrionidae Coenagrion or Enallagma 1 0.0312 0.2928 Lepidoptera Nepticulidae 6 0.0094 0.0882 Pyralidae Acentria 1 0.0140 0.1314 Trichoptera Hydroptilidae Orthotrichia 12 0.0043 0.0403 Coleoptera Curculionidae 1 0.0014 0.0131 Diptera Chironomidae 6 0.0022 0.0206

TABLE 8: Taxa ofOtsego Lake Rat Cove, July 11, 1997 94

Otsego Lake Rat Cove-July 24, 1997 TAXA Number In grams g/kg milfoil Platyhelminthes Turbellaria Tricladida Planariidae 90 0.0725 0.4495 Annelida Hirudinea Rhynchobdellida Glossiphoniidae Helobdella stagnalis 1 0.0029 0.0180 Oligochaeta Haplotaxida Naididae 14 0.0016 0.0099 Mollusca Gastropoda Basommatrophora Planorbidae Gyraulus parvus 2 0.0102 0.0632 Arthropoda Crustacea Amphipoda Talitridae Hyalella azteca 1 0.0005 0.0031 Insecta Ephemeroptera Caenidae Caenis 1 0.0004 0.0025 Odonata (Zygoptera) Coenagrionidae Coenagrion or Enallagma 2 0.0316 0.1959 Lepidoptera Nepticulidae 9 0.0107 0.0663 Pyralidae Acentria 23 0.0773 0.4792 Trichoptera Leptoceridae Oecetis I 1 0.0171 0.1060 Hydroptilidae Orthotrichia 41 0.0224 0.1389 Coleoptera Curculionidae 4 0.0052 0.0322 Diptera 1 0.0005 0.0031 Chironomidae 35 0.0122 0.0756

TABLE 9: Taxa of Otsego Lake Rat Cove, July 24, 1997 95

Otsego Lake Rat Cove-August 7, 1997 TAXA Number In grams g/kg milfoil Platyhelminthes Turbellaria Tricladlda Planariidae 220 0.1865 0.0010 Annelida Hirudinea Pharyngobdellida Erpobdellidae 2 0.0023 0.00001 Oligochaeta Haplotaxida Naididae 7 0.0009 0.000005 Mollusca Gastropoda Basommatrophora Planorbidae Gyraulus parvus 6 0.0157 0.0001 Physidae Physa integra 1 0.0130 0.0001 Mesogastropoda I Hydrobiidae Amnicola limosa 5 0.0498 0.0003 Arthropoda Arachnida Acariformes 6 0.0013 0.00001 Crustacea Amphipoda Talitridae Hyalella azteca 4 0.0014 0.00001 Insecta Ephemeroptera Caenidae Caenis 1 0.0018 0.00001

TABLE 10: Taxa of Otsego Lake Rat Cove, August 7, 1997 96

TAXA Number In grams g/kg milfoil Odonata (Anisoptera) Libellulidae 1 0.0011 0.00001 Lepidoptera Nepticulidae 8 0.0089 0.00005 Pyralidae Acent,ia 15 0.0668 0.0003 Trichoptera Leptoceridae Oecetis 9 0.0108 0.0001 Hydroptilidae Agraylea 1 0.0011 0.00001 Orthotrichia 39 0.0305 0.0002 Coleoptera Curculionidae 2 0.0031 0.00002 Diptera Chironomidae 436 0.1801 0.0009

TABLE 10 (continued): Taxa of Otsego Lake Rat Cove, August 7, 1997 97

Otsego Lake South-July 11, 1997 TAXA Number In grams g/kg milfoil IPlatyhelminthes Turbellaria Tricladida Planariidae 5 0.0001 0.0022 Mollusca Gastropoda Basommatrophora Planorbidae Gyraulus parvus 1 0.0014 0.0302 Arthropoda Arachnida Acariformes 2 0.0001 0.0022 Insecta Ephemeroptera Caenidae Caenis 10 0.0223 0.4804 Trichoptera Leptoceridae Oecetis 14 0.0399 0.8595 Hydroptilidae Orlhotnd7ia 134 0.6920 14.9074 Diptera Chironomidae 39 0.0152 0.3274

TABLE 11: Taxa of Otsego Lake South, July 11, 1997 98

Otsego Lake South-July 24, 1997 TAXA Number In grams g/kg mlifOll Platyhelminthes Turbellaria Tricladida Planariidae 36 0.0225 0.1749 Annelida Hirudinea Rhynchobdellida Glossiphoniidae Helobdella stagnalis 4 0.0772 0.6001 Oligochaeta 1 Haplotaxida Naididae I 15 0.0012 0.0093 Mollusca Gastropoda Basommatrophora j Planorbidae Gyraulus parvus 3 0.0053 0.0412 Arthropoda Crustacea Amphipoda I Talitridae I Hyalella azteca ~r015 0.0117 Insecta Ephemeroptera , I Caenidae , Caenis 1 0.0046 0358 0. 1 Lepidoptera Pyralidae Acentria I 3 I 0.0144 ~~I Trichoptera Leptoceridae Oecetis 3 0.0227 0.1765 Hydroptilidae Orthotrichia 99 0.0770 0.5986 Diptera Chironomidae 80 0.0231 0.1796

TABLE 12: Taxa of Otsego Lake South, July 24, 1997 99

Otsego Lake South-August 7, 1997 TAXA Number In grams g/kg milfoil PlatyhelmInthes Turbellaria Tricladida Planariidae 131 0.1310 0.0010 Annelida Hirudinea Pharyngobdellida Erpobdellidae 1 0.0023 0.00002 Oligochaeta Haplotaxida Naididae 4 <.0001 <.0001 Mollusca Gastropoda Basommatrophora Planorbidae Gyraulus parvus 1 0.0027 0.00002 Arthropoda Arachnida Acariformes 2 0.0003 0.000002 Crustacea Amphipoda Talitridae Hyalella azteca a 0.0051 0.00004 Isopoda Asellidae Caecidota 1 0.0007 0.00001 Insecta Ephemeroptera Caenidae Caenis 2 0.0071 0.0001

TABLE 13: Taxa of Otsego Lake South, August 7, 1997 100

TAXA Number In grams g/kg milfoil Odonata (Anisoptera) Libellulidae 2 0.0004 0.000003 Lepidoptera Pyralidae Acentria 11 0.0349 0.0003 Trichoptera Leptoceridae Oecetis 13 0.0652 0.0005 Hydroptilidae 1 0.0003 0.000002 Agraylea 19 0.0570 0.0004 Orthotrichia 27 0.0249 0.0002 Coleoptera Curculionidae 1 0.0008 0.00001 Diptera Ceratapogonidae 1 0.0005 0.000004 Chironomidae 146 0.0586 0.0004 Empididae 1 0.0015 0.00001

TABLE 13 (continued): Taxa of Otsego Lake South, August 7,1997 101

sampled members of the second generation (Harman, 1997).

The greatest diversity in species was found in Hyde Bay. At other sites, M. spicatum grew in undiversified clumps, except for at the south site which was monospecific to milfoil, though in low density.

The greatest diversity in meroplankton was found in Rat Cove and the north site. At each site, species from thirteen or fourteen different families were found (see Tables 5- 10) . Therefore, there was no correlation between meroplankton and macrophytic diversity. Members of the families Planariidae and Chironomidae were the dominant species at each of the sites.

This study provides background information of the meroplankton found to inhabit beds. The data collected seemed to indicate that Acentria, found in insignificant numbers, was probably not the cause for the lack of proliferation of M spicatum in Otsego Lake. This was a preliminary study ofAcentria populations in Otsego lake and further research should be conducted. Surveys conducted later in the season may better coincide with highest larvae densities and therefore would better evaluate the local population of these .

REFERENCES

Anon. 1986. Draft environmental impact statement for treatment of Eurasion Watermilfoil in Lake George. Lake George Park Commissions, pp. 1-107 plus appendices and ancillary materials.

Dayton, B. R. and D. R. Swift. 1987. Composition of aquatic macrophyte communities in Otsego Lake: A preliminary study, p. 68-78, In 19 th Ann. Rept. (1986). SUNY Oneonta Biological Field Station, SUNY Oneonta.

Harman, W. N. 1997. Personal Communication. SUNY Oneonta Biological Field Station, SUNY Oneonta, Oneonta, NY.

Hutchinson, G. E. 1970. The chemical ecology of three species of Myriophyllum (Angiospermae, ). Limnology and Oceanography, Vol. 15, No.1, pp. 1-5.

Merrifield, M. 1. and W. N. Harman. 1988. The , distribution and abundance of Myriophyllum (Myrtiflorae: Haloragaceae) in Otsego Lake, New York, In 20th Aim. Rept. (1987), SUNY Oneonta Biological Field Station, SUNY Oneonta, pp. 103-116.

Merritt, R. W., and K. W. Cummins (eds.) 1996. Aquatic of . Kendall/Hunt Publishing Company. Dubuque,IA.

Pennak, R. W. 1989. Freshwater invertebrates of the United States, 3rd Ed. John Wiley and Sons, Inc. New York. 102

Sanders, R. L. 1990. Recent studies in the distribution and abundance of Myriophyllum spicatum in Otsego Lake, New York. In 23 rd Ann. Rept. (1990), SUNY Oneonta Biological Field Station, SUNY Oneonta, pp. 160-164.

Stalter, A. M. 1989. The distribution and abundance ofMyriophyllum spicatum in Otsego Lake, New Yark. In 21 st Ann. Rept. (1987), SUNY Oneonta Biological Field Station, SUNY Oneonta, pp. 34-38.