Algal Flora of Some North Island, New Zealand, Lakes, Including Rotorua and RotoitiI

38 Pages·2008·18.21 MB·English

PacificScience(1974), Vol. 28, No.4, p. 467-504
Printedin GreatBritain
Algal Flora of Some North Island, New Zealand, Lakes,
Including Rotorua and Rotoiti
I
VIVIENNE CASSIE2
FROM AN EXAMINATION over a 3-yearperiod of isms were counted and identified according to
more than 370 samples, an accountis given of the method described by Cassie (1969). In the
the chief components of the phytoplankton, 3rd year, net samples were examined. Vertical
together with brief mention of neuston, auf hauls were made at selected stations from
wuchs, and benthos communities. The specific bottom to surface with a tow net having a
composition of algal classes and pollution 160-#mesh. Net samples provided apicture of
tolerance ofdifferent species are discussed. biomass,whereas jarsamples gaveinformation
From 1966 to 1969 lakes Rotorua and on abundance of smaller nannoplankton. For
Rotoitipossessedarichandvariedalgalflorain counts from concentrated jar samples, cells
which the same three species of diatoms pre rather than colonies were estimated, in an
dominatedinfluctuatingamountsthroughallor attempt to give a precise picture of total pre
part of each year. Chlorophyceae, particularly served phytoplankton. For net estimates,
Chlorococcalesand desmids,werenumerousin colonies instead of single cells were taken as
species but less prolific than diatoms in cell units for assessment of abundance. Samples
numbers, except for planktonic Mougeotia. from Lake Ohakuri and other hydroelectric
Blue-greenalgaeare knownto form noxious lakes were collected with a Mikrops tow net
blooms at times, though no such blooms (50 meshes per cm), and those from Lake
occurred within the sampling period. Dino Horowhenua were concentrated by settling
phyceae and Cryptophyceae were relatively from jars containing 300 ml oflake water.
unimportant.
The present study was undertaken to deter
mine the basic composition of the algal flora MORPHOMETRY
comprising the phytoplankton and other com
Lake Rotorua occupies a basin produced by
munitiesinseveralNorthIsland,New Zealand,
subsidence, whereas Lake Rotoiti fills a
lakes. Ofthe370samples, 260camefrom lakes
drowned v2.11ey. Both are affected by aerial top
Rotorua and Rotoiti. In addition, 91 samples
dressing and sewage effluent, though the effect
were examined from the hydroelectric lakes
ofeffluentin the latteris muchless thanin the
constructed on the Waikato River (lakes
former (Fish 1969b). Both are tectonic lakes,
Ohakuri,Atiamuri, Whakamaru, Maraetai, and
i.e., owe their origin to volcanic action. Hot
Karapiro), and 22 from Lake Horowhenua
springs occur at various places along their
near Levin(Fig. 1 and Table 1).
shores (but algae from these habitats have not
beenstudiedinthissurvey).Bothlakesare86m
above sea level. The drainage area into Lake
METHODS
Rotoiti (67 km2) is much less than that into
During the first 2 years; 200-ml samples of Lake Rdtorua. According to the Ministry
lakewaterfromlakesRotoruaandRotoitiwere of Works Kaituna Investigation Report,
preserved in Lugol's Solution and the organ- 1965, the catchment area of Lake Rotorua
is 526 km2• (Maximum recorded depth is
1 This work was supported by grants from the 44.5 m [Fish and Chapman 19691-) Lake
Fisheries Research Division, Marine Department, and Rotoiti descends more abruptly to depths
from the Botany Department, The University of
rangingfrom40to70m andhasamaximumof
Auckland. Manuscriptreceived4May 1973.
93.5 m in the center basin (Irwin 1969). The
2 DepartmentofBotany,TheUniversityofAuckland,
PrivateBag,Auckland, New Zealand. waters of Lake Rotorua that flow into Lake
467
30 HPS 28
468 PACIFIC SCIENCE, Volume 28, October 1974
N
o
, 25 5,0 Miles
FIG. 1. Southernpartofthe North Island ofNew Zealand, showing location oflakes studied and sequence of
hydroelectriclakeson Waikato River, withitsorigininLakeTaupo.
KEY: " L. Horowhenua; 2, L. Aratiatia; 3, L. Ohakuri; 4, L. Whakamaru; 5, L. Maraitai; 6, L. Waipapa;
7,L. Arapuni; 8,L. Karapiro; 9,L. Rotorua; 10,L. Rotoiti.
Rotoiti via the Ohau Channel mix with those pasture farming; whereas only part of Lake
of the latter only in the shallow basin at the Rotoiti is affected by farming, much of the
western end, after which they flow down the surrounding drainage area being clothed in
main outlet, the Kaituna River (Fish 1969b). bush. Jolly found the former to be usually
Lake Rotorua has been classified by Jolly homothermous, whereas the latter, with some
(1968) as being among those lakes directly stratification, was warm monomictic (cE.
affected by their proximity to improved Hutchinson 1957).
Algal Flora ofSome North Island Lakes-CAssIE 469
TABLE 1
SAMPLINGSTATIONSINLAKES ROTORUAAND ROTOITI
DATE STATION DESCRIPTION
LAKE ROTORUA
May 1966-May1969 A offshore(OpenLakeStation; surface,9m, 17 m)
B inshore(Kawaha Point; pooledsample)
C inshore(MokoiaIsland; pooledsample)
June 1967-May1968 A offshore(OpenLakeStation;surface, bottom)
D offshore(Hamurana-MokoiaIsland; surface, bottom)
June 1968-May1969 A offshore(OpenLake Station; bottomto surface)
LAKE ROTOITI
January-May 1967 Wrights Bay offshore(surface, 4m, 8m)
(Te PohoeBay)
June 1967-May1968 1 inshore, westend(surface,in 11 m)
2 offshore, oppositeWrights Bay(surface, in42m)
3 offshore, oppositeHauparuBay(surface,in59m)
June 1968-May1969 3 offshore, oppositeHauparu Bay(bottomto surface)
NOTE: ForlocationofRotoruastationsseeCassie(1969,fig. 1);forlocationofRotoitistations1-3seeFishand
Chapman(1969,fig. 1).
ENVIRONMENTAL FACTORS in mid-February 1966 (Irwin 1968). Maximum
andminimumtemperaturesinLakeRotorua at
Climate andTemperature
a depth of1 m were found to exceed those at
During the 3-year period, monthly rainfall the surface in November 1966 and May 1967.
varied from 0.83 inches in March 1969 to Below 1 m there was also a decrease of up to
20.87 inches in August 1967. The warmest 1.0°C in temperature with depth; but the
month also was March 1969 with 116 hours of decreaseneverexceeded1.0°Candatthemany
sunshine. Lowest insolation (70.5 hours) bathythermograph stations there was no
occurred in June 1968. There was no pro change. However, a decrease of 1.6° C was
nounced rainy season, but hours of sunshine recorded by officers ofthe Marine Department
were more numerous from January to March between surface and bottom at the O.L.S. on
than in other months. October 1967 was 27 February 1967(Cassie 1969, table 3).
notable for its warm air temperatures (4°C InLakeRotoitiIrwindetectedathermocline
above normal) and low rainfall (1.4 inches between 10 and 20 m where temperatures
below normal [N. G. Robertson, personal ranged from 20° to 16°C (a gradient 0.4° C
communication]). per m). Hypolimnion temperatures ranged
In Lake Rotorua surface water temperatures from 11.9° to 12.8°C. Jolly (1968) recorded
at the open lake station (O.L.S.) were also surfaceandbottomwintertemperaturesinLake
higher in November 1967 than ~t any time in Rotoiti as being 11.0°C and 10.5°C, respec
the preceding and following years. Figures tively. In Lake Rotorua Irwin found that
from thefirst sampling yeararegiveninCassie thermal stratificationwas ill-defined or absent;
1969, fig. 2. Subsequent data show that the whereasinLakeRotoitistratificationdidoccur.
lowest temperaturewas 8.6° Con22 July 1968
and the highestwas 21.4°C on 12March 1968
ChemicalConditions
(G. R. Fish, personal communication).
Surface temperatures in Lake Rotorua The1955-1956valuesquotedbyJolly(1968)
(measured by bathythermograph in daylight) for ammonia-nitrogen and phosphate were
were found to vary from 13° to 14°C (2 to fairlylow; whereas nitratenitrogenwas hardly
4 May 1967) and varied from 22,50 to 24.5°C detectable in either lake. Silicate ranged from
30-2
470 PACIFIC SCIENCE, Volume 28, October 1974
TABLE 2
NUMBERS OF SPECIESIDENTIFIED FROMDIFFERENTALGAL CLASSES ANDHABITATS
TOTALNUMBER
PLANKTON AUFWUCHS BENTHOS IDENTIFIED
Chlorophyceae 44 7 51
Xanthophyceae 2 2
Chrysophyceae 7 1 8
BaciIIariophyceae 8 11 5 24
Euglenophyceae 1 1 4 6
Dinophyceae 6 6
Cryoptophyceae 1 1
Myxophyceae 10 3 5 18
Total 79 22 15 116
2-5 mg/liter in Lake Rotoiti and from 1 DissolvedOxygen
6mg/liter in Lake Rotorua-Iow values for
As with the surface waters of other New
thermal waters (Jolly 1968: 240). Fish (1969b)
Zealand lakes, those of Rotorua and Rotoiti
reported that in Lake Rotorua during the last
showed a high percentage saturation at most
2decades therehas beenatremendous incre2se
seasons, especially in spring when there was a
in the forces promoting eutrophication, due
high rate ofphotosynthesis. Jolly (1968) ga:e
particularly to land development, c~using
the following figures to indicate the range 111
erosion and water runoff. The populatIon of
percentagesaturationofdissolvedoxygenfrom
Rotorua City has increased greatly, and
surface to bottom in the two lakes: Lake
phosphate-phosphorus and. nitrate-nitr~~en
Rotoiti-surface 122-90, bottom 130-29; Lake
havebeenretainedinthelakeInvastqu?ntltIes.
Rotorua-surface 138-95, bottom 130-94.
As a result the standing crop of organisms is
During March and April in Lake Rot~iti,
now much greater.
minimal values for oxygen were recorded Just
Data on the phosphate-phosphorus, nitrate
below the thermocline. In the hypolimnion a
nitrogen, and ammonia-nitrogen content of
mean annual minimum of dissolved oxygen
Lake Rotorua from June 1967 to May 1968
was estimatedbyJollyas being3.1 ppm. More
(Fish1969b: table 1) showthatthe totalinflow
recently, in 1967-1968, Fish(1969a) found the
of these nutrients greatly exceeds the surface
mean annual minimum in the hypolimnion to
outflow.Themaximumamountofphosphate-P
be no greater than 0.08 ppm. A comparison
recordedbyFish(7,692 kg or22percent) came
between the figures of Jolly (1968) and those
from the Hamurana Stream. Nitrate-N was
ofFish(1969a) showsthatminimalvalueswere
most abundant from the Awahou Stream
lower in 1967-1968 than in 1956-1957. In
(30,583kgor28percent).Thebulkofa~monia­
1956-1957 the dissolved oxygen in ppm in
N (95,500 kg or 66.5 percent) flowed Into the
Lake Rotorua ranged from 12.4 to 9.0 (Jolly
lake through the Waiohewa Stream. The
1968);in1967-1968thosevalues were11.2-3.5
amount of phosphate-P and ammonia-N
(Fish 1969a).
entering the lake from sewage outflow during
the same period was smaller (14.2 percent and
19.9 percent, respectively). No nitrate-N was COMMUNITIES
P!?Jtoplankton
recorded from this source. It seems likely, ac
cording to Fish, that agricultural development Theappendixatthe end ofthiswork consti
provides more nutrients that promote eutro tutes a list of all algae identified during the
phication than does sew~ge inflow. F~rther, survey, together with their abundance on a
during periods of flood111g the quantIty of 1-to-5 scale (Cassie 1961). The symbols p, a,
nutrients in the lake can increase within a few and b indicate their habitat: whether phyto
days by two or more orders ofmagnitude. plankton, aufwuchs, or benthos. Records for
Algal Flora ofSome North Island Lakes-CAssIE 471
FIG. 2. Melosira grantllata Ralfs. Auxospore. Film FIG.3.PeridinicumstriolattlmPlayf.FilmS/12A. x1500.
14/24A. x2135.
a and b are fragmentary. Table 2 indicates the phyceae, Dinophyceae, and Chrysophyceae
distributionofspeciesamongthedifferentalgal seldom achieving ecological importance, at
classes. The phytoplankton component is by leastinpreservedsamples.Ingeneral, no single
far the largest, mainly because it was the phytoplankter dominated to the exclusion of
principal object of study. Numbers of species all others. Over the 3-year sampling period
in each category are therefore merely an thepatternofabundanceofthedifferentdomi
interim guide to those actually present. nants and subdominants (5 and 4 on the
Seventy-nineofthetotallistof116specieswere abundance scale in the appendix) did not vary
found to lead a planktonic existence. These greatly.
were not necessarily obligate phytoplankters, Fishand Chapman(1969) notedthat greatest
but were the ones that most characteristically phytoplankton production in Lake Rotorua
occupiedthathabitat.Withinthephytoplankton occurs in the northeastern quadrant where
communitythe chlorophycean componentwas waters move toward the main outlet, Ohau
the strongestonewhen numbers ofspecies are Channel. These workers have also published
considered. Only rarely did green algae domi maps showing beds of submerged Lagaro
nate, however. The most abundant were siphonandElodeathatoccuratintervalsnearthe
Bacillariophyceae (Cassie 1969), with Myxo- western shore ofthelake. Lowercell counts in
472 PACIFIC SCIENCE, Volume 28, October 1974
samples from inshore western waters are con phytoplankton bloom. Very frequent were
sistentwiththefactthatFitzgerald(1969)found rapidly moving uniflagellateChromulina sp., no
an antagonism between aquatic macrophytes more than 6 to 12p,in diameter. Itis not con
and competing phytoplankton. (Cf. Cassie fined to theneuston, however, since specimens
1969, who recorded lower cell numbers at havebeenobservedinfresh subsurfacesamples
Kawaha Point.) It is interesting to note in from both lakes. Small flagellated chryso
this connection that Mitchell (1971) found monads are known to become attached to the
in Tomahawk Lagoon (no. 2) on the south surface film, surround themselves with an
side of Otago Peninsula that large crops envelope, and orient their chromatophores at
of either phytoplankton or macrophytes right angles to the incident light. When light
were always present, though never both rays are concentrated on them, the cell acts as
together. alensfromwhichthelightis reflected(Ruttner
R. M. Cassie (personal communication) has 1963: 136). It could be that the phenomenon
shownbystatisticalanalysis ofa detailedsetof observedonLakeRotoitiwasasimilarone,but
samples taken over 24 hours that the phyto the exact species responsible for the present
plankton population of Lake Rotorua is rela phenomenon was not identified. Although 12
tively homogeneous despite differences due to otherspecieswereobservedinthesample,none
depths and stations. Melosira granulata (Fig. 2) was as abundant as the minute Chromulina.
in particular shows a fairly consistent vertical Other species, including Anabaena flos-aquae,
homogeneity in distribution. By comparison Melosiradistans,Mougeotiasp.(narrowfilaments),
Jolly (1959) found in her net samples that Rhizosoleniaeriensis,Cystodiniumcornifax,Asterio
Melosira was by far the most abundant phyto nella formosa, and Bot,:yococcus braunii are all
plankter and Chlorophyceae were subordinate known to occur in subsurface phytoplankton.
though several genera, including Mougeotia, (See Cassie 1969: figs. 4, 6, 8, 9.)
Cosmarium, Dicryosphaerium, Spon4Ylosium(prob Other species common or occasional in the
ably including Sphaerozosma), and Closterium, phytoplankton at various times of the year
were conspicuous. All but the first two were included Microrystis aeruginosa, Anabaena circi
representedbysmallnumbers. Jollyalso found nalis, Pandorina morum, Trachelomonas volvocina,
Staurastrum, Dinobryon, and Peridinium (prob Dinobryon y€ lindricum, and Nephrorytium agardhi
ably P. striolatum, Fig. 3) to be moreabundant anum(Figs. 4-9).
in Lake Rotoiti. Asterionella was insignificant. Staurastrum and Staurodesmus were nearly
ItappearsfromacomparisonofJolly'Srecords always present, though seldom in large
with those of the present survey th3t, apart numbers; e.g., Staurastrum floriferum (Fig. 4),
fromthescarcityofAsterionella,theproportion S. leptocladum var. insigne (Fig. 10), S. sexangu
of most of the planktonic algae has remained lare (Fig. 11), and Staurodesmus unicornis V2!.
approximately the same. Two chlorophycean ceylonensis (Fig. 12). Staurodesmus convergens var.
genera not recorded by Jolly but which laportei (Fig. 13) has been found to date only
achieveddominanceattimes between1967and in the "hydroelectric" lakes on the Waikato
1969 were Actinotaenium pyramidatum and RiverandinLakeRotoma(nearLakeRotoiti).
Actinastrumhantschii. Cyclotella stelligera (Fig. 14), though dominant
A single fresh neuston (surface film) sample once in Lake Rotorua, was usually more
collected in September 1969 from the surface abundant in Lake Rotoiti.
of Lake Rotoiti between Wrights (Te Pohoe)
Bay and Cherry Bay was examined. Here the
Aufwuchs
surface water displayed parallel rows of
golden brown organisms which, on micro The aufwuchs community, i.e., organisms
scopic examination, consisted of a number of attached to ormoving upon aliving substrate,
normally planktonic species intermingled with occursinlakes Rotoruaand Rotoitimostcom
masses of winged pine pollen embedded in monly on the macrophytes Lagarosiphon mqjor
clumps of amorphous golden brown organic and Nitella hookeri. A few samples have been
matter, which could have been a disintegrated examinedfromthelittoralzone(shallowinshore
Algal Flora ofSome North Island Lakes-CAssIE 473
FIG. 4. Microrystisaeruginosa Klitz. and Staurastruntfloriferttnt (West & West) Brook. Film 14/19A. x3400.
FIG. 5. AnabaenacircinalisRabenh. Film 9/31. x3600.
474 PACIFIC SCIENCE, Volume 28, October 1974
areas up to 5m deep). Twenty-two species of
algae have been identified from the aufwuchs
(Table 2). Diatoms predominate (11 species)
and ChloropfDiceae are abundant (7 species).
There was no opportunity to study seasonal
behavior of the principal species. Many more
will doubtless be revealed by some intensive
investigations. Among the diatoms, pennate
forms are the most conspicuous. Epithemia
sorex, rather like a set offalse teeth when two
adjacent fructules are seen in girdle view
(Fig. 15), is one of the commonest (cf. Flint
1938, who noted a winter dominance and a
year-roundoccurrenceofE.sorexinLakeSarah,
Cass District, S. Island, New Zealand; and
Castenholz 1960, who recorded this species in
Alkali Lake, Lower Grand Coulee, Washing
ton, as a prominent member of a pennate
diatom community during autumn).
Epithemia zebra (Fig. 16) is less frequently
encountered.
Epithemia and Eunotia sp. attach themselves
firmly to leafand stem apices of Lagarosiphon
and Nitella. Ofthe unattachedspecies, Melosira
lineata(3 to 10cellsperchain, Figs. 17, 18) and
Fragilariacrotonensis(Fig. 19)arelessfrequently
encountered. Fragilaria virescens (Fig. 20) may
FIG. 6.Pandorinamorttm(Mull.)Bory.Film9/28. x4000.
FIG. 7. Trachclomonasvolvocina(Ehr.)andAsterioncllaformosaHass. Film9/17A. x4000.
Algal Flora ofSome North Island Lakes-CAssIE 475
FIG. 8. Dinob~yon cylindriCtimva!. alpinum(1mb.) Bacbm. Film12/16. x1125.
also occur. Many different small green algae,
including Closteriumparvulum and C. aciculare
(Figs. 21, 22), Scenedesmus, Kirchneriella, Cruci
genia(Fig. 23), Selenastrum, and Mougeotia(wide
cells), are intermingled with normally plank
tonic species such as Melosira granulata, M.
distans, Mougeotia(narrow cells), and numerous
species of Staurastrum. Filaments of LyngbJla
frequently enmesh fronds of the macrophyte
Lagarosiphonnearthesurface. Othersworthyof
mention among the aufwuchs community are
Rhopalodia gibba, Ankistrodesmus falcatus, and
the desmid Sphaerozosma aubertianum vaL com
pressum, and Tabellariaflocculosa(Figs. 24-26).
Equallycommonamongaufwuchsorphyto
planktonareEudorinaelegans,Pediastrumduplex,
and P. boryanum (Figs. 27-29), as well as
Ankistrodesmusand Sphaerozosma. The position
of Peroniella planktonica (Fig. 30) is hard to
categorize, since It is planktonic merely by
growing as an epiphyte and being carried up
into thephytoplanktonbyits filamentous host.
A specimen ofNitella hookeri collectedfrom
Cherry Bay by B. Coffey showed a growth at
branch apices ofanalgacloselyresembling the
FIG. 9. Nepbroeytitlm agardbianllm Nag. Film 6j20A.
x4000. genus Thamniochaete (cf. Bourrelly 1966). The
476 PACIFIC SCIENCE, Volume 28, October 1974
FIG. 10.Staurastrumleptoc/adiumvar. insigneWest & West. Film15/10. x1800.
FIG. 11.Sta!lrastrumsexangulare(Bulnh.) Lund. Film12/11A. x1275.
l2\LIO;U;.~u:::z:zEmlU,l1l!.nu::::'SiS