**3. Results**

## **3.1 Bioluminescence measured with MOORDEX**

A winter maximum and summer minimum in bioluminescence was measured at SCI in contrast to a maximum in the spring and minimum in the fall in San Diego Bay (SDB) (Figure 2). Mean monthly bioluminescence at SCI varied little from August 1993 - February 1996 except during a red tide in January 1995 (maximum of 2 x 108 photons s-1 ml-1 seawater measured in January 1995) which persisted through April (Figure 2). In contrast, seasonal changes in bioluminescence were observed in SDB. Maximum bioluminescence (1 x 108 photons s-1 ml-1 or greater) was measured from March through September for 1993, May through June for 1994, December through May for 1995, and March through April for 1996. Minimum values less than 1 x 108 photons sec-1 ml-1) were measured in the winter (Figure 2) (Lapota et al., 1997).

### **3.2 Bioluminescent plankton at San Clemente Island**

The numbers of bioluminescent dinoflagellates were typically lower at SCI than at SDB and ranged from 3 - 211 cells L-1 of seawater from August 1993 through December 1994 (Figure 3). In contrast, in SDB, maximum numbers of bioluminescent dinoflagellates were collected during the spring-summer months (2430 - 17,216 cells L-1). Minimal numbers of bioluminescent dinoflagellates were collected in the winter in SDB. At SCI, the principal species observed were *G. polyedra* and several species of *Protoperidinium.* A red tide was first observed in January 1995 and persisted through April 1995. Bioluminescence during this event increased approximately 10 times above former levels for both SDB and SCI. Total and bioluminescent dinoflagellates increased to 16,727 cells L-1 and 15,939 cells L-1, respectively in January 1995 at SCI (Figure 3). Cell numbers remained high through April 1995. At SCI bioluminescent dinoflagellates comprised a major percentage of total dinoflagellates collected (Figure 4).

values for each species tested for all seasons were calculated. The Student's t test for comparison of two means was used to calculate significant differences between means of cells within species for all seasons. Critical values of the Student's t distribution were

Nitrate and Chl *a* levels were obtained from archived CalCOFI data bases from 1994 - 1996 for the Southern California Bight and were averaged along CalCOFI lines 90 and 93 which extend offshore west of San Diego to the north and south of SCI (Hayward et al. 1996). Nitrates (m L-1) and Chl *a* (g L-1) along each of the CalCOFI transit lines 93.26 to 93.45 and 90.28 to 90.53 were averaged from the surface to a depth of 50 m, seasonally (fall, winter, spring, summer), from spring 1994 through spring 1996. These data were used to calculate correlations with seasonal means of bioluminescence cell-1 of the photosynthetic dinoflagellate *Pyrocystis noctiluca* and the heterotrophic dinoflagellate *Protoperidnium pellucidum*. Nutrient data was lagged by one season to calculate correlation coefficients with mean bioluminescence cell-1. The Student t-test was used to determine significant differences among seasonal bioluminescence means for *Gonyaulax, Ceratium, Pyrocystis*, and

A winter maximum and summer minimum in bioluminescence was measured at SCI in contrast to a maximum in the spring and minimum in the fall in San Diego Bay (SDB) (Figure 2). Mean monthly bioluminescence at SCI varied little from August 1993 - February 1996 except during a red tide in January 1995 (maximum of 2 x 108 photons s-1 ml-1 seawater measured in January 1995) which persisted through April (Figure 2). In contrast, seasonal changes in bioluminescence were observed in SDB. Maximum bioluminescence (1 x 108 photons s-1 ml-1 or greater) was measured from March through September for 1993, May through June for 1994, December through May for 1995, and March through April for 1996. Minimum values less than 1 x 108 photons sec-1 ml-1) were measured in the winter (Figure 2)

The numbers of bioluminescent dinoflagellates were typically lower at SCI than at SDB and ranged from 3 - 211 cells L-1 of seawater from August 1993 through December 1994 (Figure 3). In contrast, in SDB, maximum numbers of bioluminescent dinoflagellates were collected during the spring-summer months (2430 - 17,216 cells L-1). Minimal numbers of bioluminescent dinoflagellates were collected in the winter in SDB. At SCI, the principal species observed were *G. polyedra* and several species of *Protoperidinium.* A red tide was first observed in January 1995 and persisted through April 1995. Bioluminescence during this event increased approximately 10 times above former levels for both SDB and SCI. Total and bioluminescent dinoflagellates increased to 16,727 cells L-1 and 15,939 cells L-1, respectively in January 1995 at SCI (Figure 3). Cell numbers remained high through April 1995. At SCI bioluminescent dinoflagellates comprised a major percentage of total dinoflagellates

calculated using n-2 degrees of freedom.

**3.1 Bioluminescence measured with MOORDEX**

**3.2 Bioluminescent plankton at San Clemente Island** 

**2.2 Nutrient and chlorophyll data** 

*Protoperidinium* species.

(Lapota et al., 1997).

collected (Figure 4).

**3. Results**

Fig. 2. Mean monthly bioluminescence trends at San Diego Bay and San Clemente Island from 1992-1996.

Fig. 3. The abundance of *Protoperidinium* and *Gonyaulax* dinoflagellates at San Clemente Island from 1993-1996.

Seasonal Changes of Bioluminescence in

Photosynthetic and Heterotrophic Dinoflagellates at San Clemente Island 33

only 10% of all months. During the red tide in the winter and spring of 1995, *Gonyaulax*  contributed 59%, 42%, 58%, 48%, and 27% of all bioluminescence for the months of January through May 1995, respectively (Figure 6). The open ocean bioluminescent dinoflagellate *Pyrocystis noctiluca* was also found in monthly samples. *Protoperidinium curtipes*, *P. depressum*, *P. divergens*, *P. leonis*, and *P. steinii* were present in the spring and summer

months while *Gonyaulax* became more prevalent in the fall and winter months.

Fig. 6. (a) Seasonal differences in *Protoperidinium pellucidum* mean bioluminescence and

Three to 6 recurrent species of dinoflagellates were usually found in the collected plankton samples for each season. In 5 of the 9 seasons, more than 45 cells isolated proved to be luminescent and were identified to species level. In all, bioluminescence from 469 identified cells representing 5 genera and 13 species were measured (Table 1). Cells of *Gonyaulax polyedra, Ceratium fusus, Pyrocystis noctiluca*, and the heterotroph *Protoperidinium pellucidum* were found more frequently in plankton collections than other species, and from these data,

Mean light output cell-1 for all dinoflagellates is listed in Tables 2,3,4,5 and in Figures 6-9. The mean light output for all quarters for all species is listed in Table 2 and ranges from 1.6e8 photons cell-1 for *Ceratium fusus* to 1.8e10 photons cell-1 for *Pyrocystis noctiluca*. *G. grindleyi* was the brightest species of *Gonyaulax* tested and was approximately 3 times brighter than *G. polyedra* (Table 2). Cells of species of *Protoperidinium* ranged from 1 to 4e9

mean Chl *a* for waters surrounding San Clemente Island 1994-1996.

seasonal mean bioluminescence cell-1 was determined.

**3.4 Light output from Dinoflagellates** 

photons cell-1 (Tables 2, 3; Figure 6a).

Fig. 4. Total and bioluminescent dinoflagellate cells collected monthly at San Clemente Island from 1993-1996.

#### **3.3 Light budget analysis**

The light budget analysis (number of cells L-1 of each bioluminescent species multiplied by the mean light output cell-1 and then adjusted by dividing the species light contribution by the sum of all bioluminescence from all species) indicated that the *Protoperidinium* dinoflagellates produced most of the bioluminescence (Figure 5).

Fig. 5. Bioluminescence produced by each species (photons liter-1) monthly at San Clemente Island from 1993-1996.

*Gonyaulax* spp. and *Ceratium fusus* contributed less. *Protoperidinium* contributed more than 80% of all bioluminescence for 60% of all months (30 months) and more than 50% of all bioluminescence for 77% of all months. In contrast, *Gonyaulax* contributed 80% of all bioluminescence for just 1 month (3.3% of all months) and 50% of all bioluminescence for

Fig. 4. Total and bioluminescent dinoflagellate cells collected monthly at San Clemente

dinoflagellates produced most of the bioluminescence (Figure 5).

The light budget analysis (number of cells L-1 of each bioluminescent species multiplied by the mean light output cell-1 and then adjusted by dividing the species light contribution by the sum of all bioluminescence from all species) indicated that the *Protoperidinium*

Fig. 5. Bioluminescence produced by each species (photons liter-1) monthly at San Clemente

*Gonyaulax* spp. and *Ceratium fusus* contributed less. *Protoperidinium* contributed more than 80% of all bioluminescence for 60% of all months (30 months) and more than 50% of all bioluminescence for 77% of all months. In contrast, *Gonyaulax* contributed 80% of all bioluminescence for just 1 month (3.3% of all months) and 50% of all bioluminescence for

Island from 1993-1996.

Island from 1993-1996.

**3.3 Light budget analysis** 

only 10% of all months. During the red tide in the winter and spring of 1995, *Gonyaulax*  contributed 59%, 42%, 58%, 48%, and 27% of all bioluminescence for the months of January through May 1995, respectively (Figure 6). The open ocean bioluminescent dinoflagellate *Pyrocystis noctiluca* was also found in monthly samples. *Protoperidinium curtipes*, *P. depressum*, *P. divergens*, *P. leonis*, and *P. steinii* were present in the spring and summer months while *Gonyaulax* became more prevalent in the fall and winter months.

Fig. 6. (a) Seasonal differences in *Protoperidinium pellucidum* mean bioluminescence and mean Chl *a* for waters surrounding San Clemente Island 1994-1996.

## **3.4 Light output from Dinoflagellates**

Three to 6 recurrent species of dinoflagellates were usually found in the collected plankton samples for each season. In 5 of the 9 seasons, more than 45 cells isolated proved to be luminescent and were identified to species level. In all, bioluminescence from 469 identified cells representing 5 genera and 13 species were measured (Table 1). Cells of *Gonyaulax polyedra, Ceratium fusus, Pyrocystis noctiluca*, and the heterotroph *Protoperidinium pellucidum* were found more frequently in plankton collections than other species, and from these data, seasonal mean bioluminescence cell-1 was determined.

Mean light output cell-1 for all dinoflagellates is listed in Tables 2,3,4,5 and in Figures 6-9. The mean light output for all quarters for all species is listed in Table 2 and ranges from 1.6e8 photons cell-1 for *Ceratium fusus* to 1.8e10 photons cell-1 for *Pyrocystis noctiluca*. *G. grindleyi* was the brightest species of *Gonyaulax* tested and was approximately 3 times brighter than *G. polyedra* (Table 2). Cells of species of *Protoperidinium* ranged from 1 to 4e9 photons cell-1 (Tables 2, 3; Figure 6a).

Seasonal Changes of Bioluminescence in

4.1e9; 9 cells

1.6e9; 11 cells

7.9e8; 3 cells

3 cells

*G. spin.* 2.2e8; 7

cells

3.6e8; 9 cells

Table 3. Light output for other *Protoperidinium* spp. (mean photons cell-1) 1994 – 1996.

**Species Spr'94 Sum'94 Fall'94 Win'95 Spr'95 Sum'95 Fall'95 Win'96 Spr'96** 

6.8e8; 2 cells

19 cells

**Cells Spr'94 Sum'94 Fall'94 Win'95 Spr'95 Sum'95 Fall'95 Win'96 Spr'96** 

2.1e7; 1 cell

Table 4. Light output for other *Gonyaulax* species (mean photons cell-1) 1994 – 1996.

5.7e7; 7 cells

8.4e8; 6

Table 5. Light output for *Ceratium fusus* (in mean photons cell-1)1994-1996.

1.1e8; 12 cells

*P. stei.* 4.3e8;

*G. grind.* 8.9e8; 8

*G. polyed.* 9.8e7 ;

*P. de.* 1.6e9;

*P. di.* 4.4e9;

*P. cur.* 5.9e9;

*P. leo* 6.3e9;

*G. poly.* 6.2e8;9

**Small cells** 

**Large cells** 

cells

7 cells

8 cells

9 cells

4 cells

Photosynthetic and Heterotrophic Dinoflagellates at San Clemente Island 35

**Species Spr'94 Sum'94 Fall'94 Win'95 Spr'95 Sum'95 Fall'95 Win' 96 Spr'96** 

1.8e9; 3 cells 3.6e9; 2 cells

5.2e8; 12 cells

8.4e8; 12 cells

4.2e8; 14 cells

8.4e7; 13 cells

cells

cells

7.3e8; 15 cells

4.2e8; 11 cells

1.6e8; 19 cells

6.3e8; 15 cells

2.3e8; 3 cells

1.3e9; 5 cells

2.5e9; 5 cells

1.9e9; 3 cells


Table 1. Bioluminescent dinoflagellate species surveyed in study.


Table 2. Comparative light output for all species 1994-1996. Listing is by mean light output.

*Ceratium fusus* (small cells) Fall'94, Win'95; Spr'95, Fall'95; Win'96,

*P. pellucidum* Sum'94, Fall'94; Win'95, Spr'95; Sum'95,

*Pyrocystis noctiluca* Spr'94, Sum'94 ; Fall'94, Win'95 ; Sum'95,

Table 2. Comparative light output for all species 1994-1996. Listing is by mean light output.

Spr'96

Fall'95; Win'96, Spr'96

Fall'95; Win'96, Spr'96

**Standard Deviation Number of cells** 

**tested** 

**Species Season Tested**  *G. grindley* Fall'94, Win'95

*G. spinifera* Sum'95, Fall'95

*P. divergens* Spr'94, Sum'94 *P. leonis* Spr'94, Spr'95

Table 1. Bioluminescent dinoflagellate species surveyed in study.

**output** 

**(photons cell-1)** 

*Ceratium fusus (***small cells)** 1.5e8 1.9e8 52 *Gonyaulax polyedra* 2.4e8 2.2e8 56 *Gonyaulax spinifera* 6.1e8 4.5e8 19 *Gonyaulax polygramma* 6.3e8 4.2e8 36 *Ceratium fusus* **(large cells)** 8e8 5.7e8 26 *Gonyaulax grindleyi* 8.5e8 5.2e8 10 *Protoperidinium steinii* 1e9 1.1e9 5 *Protoperidinium pellucidum* 1.2e9 1e9 112 *Protoperidinium divergens* 2.8e9 3.9e9 19 *Protoperidinium depressum* 3.1e9 2.8e9 18 *Protoperidinium curtipes* 4e9 4.7e9 17 *Protoperidinium leonis* 4.4e9 3e9 7 *Pyrocystis noctiluca* 1.8e10 9.7e9 105

*P. steinii* Fall'94 *Noctiluca miliaris* Spr'95

**Species Mean light** 

*G. polyedra* Win'95, Spr'95; Fall'95, Win'96

*G. polygramma* Spr'94, Fall'95, Win'96

*C. fusus* (large cells) Fall'95, Win'96; Spr'96 *Protoperidinium curtipes* Spr'94, Sum'94; Spr'96 *P. depressum* Spr'94, Sum'94; Win'96


Table 3. Light output for other *Protoperidinium* spp. (mean photons cell-1) 1994 – 1996.


Table 4. Light output for other *Gonyaulax* species (mean photons cell-1) 1994 – 1996.


Table 5. Light output for *Ceratium fusus* (in mean photons cell-1)1994-1996.

Seasonal Changes of Bioluminescence in

**Seasons between years Fall'94 - Fall'95** 

\*= not significant

fall (Table 8).

1996.

**3.4.2** *Protoperidinium* 

between 1994 and 1995.

Photosynthetic and Heterotrophic Dinoflagellates at San Clemente Island 37

Significant differences in mean cell light output were measured among *Gonyaulax polyedra, G. spinifera*, and *G. polygramma* (Table 8). Cells of *G. polyedra* of fall '95 produced significantly more light than cells tested previously in the winter and spring '95 (p < 0.001; Table 8). Cells tested in the winter '96 were significantly brighter than the previous spring '95. Yearly differences were also observed between both winters of '95 and '96 where '96 cells > '95 cells. The fall '95 cells of *G. spinifera* exhibited more bioluminescence than in the summer while winter '96 *G. polygramma* cells were measurably brighter than earlier in the

*G. polyedra*

*G. spinifera*

*G. polygramma*

Table 8. Significant differences of light output seasonally in *Gonyaulax* species from 1995 -

The winter '95 *Protoperidinium pellucidum* cells were observed to produce more bioluminescence than cells from summer '94 and fall '94 (Table 6). They were not significantly different than cells tested in spring '95. Cells of *P. pellucidum* in the fall '95 were significantly brighter than cells tested in summer '95, and spring '96, but not winter '96 (Table 6). A significant seasonal difference between years was observed for the fall quarters. These cells were also significantly brighter in Fall '95 than in the fall '94 (Table 6). Significant differences in light output were not found for summer, winter, and spring

**Spr'94 - Spr'96 Spr'96 > Spr'94 p < 0.1 Sum'94 - Sum'95** Sum'95 > Sum'94 p< 0.6\* **Fall'94 - Fall'95** Fall'95 > Fall'94 p< 0.5\* **Win'95 - Win'96** Win'96 > Win'95 p < 0.2

**Win'95 - Spr'95** P<0.8 n.s. **Fall'95 – Win'95** Fall > Win p < 0.001 **Fall '95 – Spr'95** Fall > Spr p < 0.001 **Win'96 – Win'95** Win'96 > Win'95 p < 0.001 **Win'96 – Spr'95** Win > Spr p < 0.001 **Win'96 – Fall'95** P < 0.9 n.s.

**Fall'95 – Sum'95** Fall > Sum P < 0.001

**Win'96 – Fall'95** Win > Fall P < 0.2


\*levels of significance for two-tail student t test

Table 6. Significant differences of light output seasonally in *Protoperidinium pellucidum* from 1994 – 1996\*.

#### **Seasons between years**


n.s. = not significant

#### **3.4.1** *Pyrocystis noctiluca*

Significant differences in mean bioluminescence cell-1 were observed between spring '94 and summer '94, between spring '94 and fall '94, between spring '94 and winter '95, and between spring '94 and spring '96 (Table 7). Spring '96 cells produced more bioluminescence than spring '94 cells as did winter '96 cells when compared to winter '95 cells (Table 7). *Gonyaulax*  spp**.** 


Table 7. Significant differences of light output seasonally in *Pyrocystis noctiluca* from 1994 – 1996 (\* = not significant).


#### **Seasons between years Fall'94 - Fall'95**

\*= not significant

36 Bioluminescence – Recent Advances in Oceanic Measurements and Laboratory Applications

Table 6. Significant differences of light output seasonally in *Protoperidinium pellucidum* from

Significant differences in mean bioluminescence cell-1 were observed between spring '94 and summer '94, between spring '94 and fall '94, between spring '94 and winter '95, and between spring '94 and spring '96 (Table 7). Spring '96 cells produced more bioluminescence than spring '94 cells as did winter '96 cells when compared to winter '95 cells (Table 7). *Gonyaulax* 

**Sum'95** P<0.6\* P<0.8\* P<0.7\*

**Win'96** P<0.2 P<0.5\*

Table 7. Significant differences of light output seasonally in *Pyrocystis noctiluca* from 1994 –

**Fall'95** P<0.5\* P<0.8\* P<0.3 P<0.7\*

**Spr'94 Sum'94 Fall'94 Win'95 Spr'95 Sum'95 Fall'95 Win'96 Spr'96** 

**Sum'94 Fall'94 Spr'95** 

**Sum'95 Win'96 Spr'96** 

p < 0.01 n.s. p < 0.01

p< 0.10 p < 0.001 n.s.

**Win'95 bioluminescence is significantly greater** 

**Fall'95 bioluminescence is significantly greater** 

**Seasons between years** 

n.s. = not significant

**Sum'94** p<0.3

**Spr'96** p<0.1

1996 (\* = not significant).

**Win'95** p<0.3 P<0.9\* **Spr'95** P<0.6\*

spp**.** 

**3.4.1** *Pyrocystis noctiluca*

\*levels of significance for two-tail student t test

**Sum'94 - Sum'95 bioluminescence n.s.** 

**Win'95 - Win'96 bioluminescence** n.s. **Spr'95 - Spr'96 bioluminescence** n.s.

**Fall'94** p<0.2 P<0.4\* P<0.6\*

**Fall'94 - Fall'95 bioluminescence** Fall'95 > Fall'94; p < 0.001

**than** 

**than** 

1994 – 1996\*.

Significant differences in mean cell light output were measured among *Gonyaulax polyedra, G. spinifera*, and *G. polygramma* (Table 8). Cells of *G. polyedra* of fall '95 produced significantly more light than cells tested previously in the winter and spring '95 (p < 0.001; Table 8). Cells tested in the winter '96 were significantly brighter than the previous spring '95. Yearly differences were also observed between both winters of '95 and '96 where '96 cells > '95 cells. The fall '95 cells of *G. spinifera* exhibited more bioluminescence than in the summer while winter '96 *G. polygramma* cells were measurably brighter than earlier in the fall (Table 8).


Table 8. Significant differences of light output seasonally in *Gonyaulax* species from 1995 - 1996.

#### **3.4.2** *Protoperidinium*

The winter '95 *Protoperidinium pellucidum* cells were observed to produce more bioluminescence than cells from summer '94 and fall '94 (Table 6). They were not significantly different than cells tested in spring '95. Cells of *P. pellucidum* in the fall '95 were significantly brighter than cells tested in summer '95, and spring '96, but not winter '96 (Table 6). A significant seasonal difference between years was observed for the fall quarters. These cells were also significantly brighter in Fall '95 than in the fall '94 (Table 6). Significant differences in light output were not found for summer, winter, and spring between 1994 and 1995.

Seasonal Changes of Bioluminescence in

Photosynthetic and Heterotrophic Dinoflagellates at San Clemente Island 39

Maximum bioluminescence in *Protoperidinium pellucidum, Pyrocystis noctiluca, Ceratium fusus*, and *Gonyaulax polyedra* was observed in either fall or winter for 1994–1996. Maximum bioluminescence cell-1 in *P. pellucidum* occurred in winter 1995 and during the following fall. Bioluminescence in this species was lower in summer '94 and again in summer '95 (Figures 6a,b). The percent of peak bioluminescence (the peak refers to maximum bioluminescence measured in winter '95 and fall '95) varies with season with values as low as 30% for summer '94 and 20% for summer '95 (Figure 6b). Because *Protoperidinium* dinoflagellates are nutritionally dependent on other algal species, any change of algal biomass in waters adjacent to SCI might impact the growth, maintenance and luminescent potential of *Protoperidinium*. Extracted Chl *a* showed a similar periodicity as did mean bioluminescence cell-1 in *P. pellucidum* from summer '94 through summer '95. Maximum Chl *a* and mean bioluminescence cell-1 levels increased in winter 1995 and in spring 1995 (Figure 7a). The seasonal mean bioluminescence cell-1 and the seasonal mean Chl *a* in the waters off SCI were positively correlated (Figure 6c). Bioluminescence in *P. pellucidum* was not significantly different between winter and spring quarter 1995, but was significantly brighter than the

**3.4.4 Seasonal trends of dinoflagellate bioluminescence, nitrates, and Chl** *a*

preceding summer and fall quarters and the ensuing summer 1995 quarter (Table 6).

Fig. 6. (b) 1994 to 1996 year comparison of percent of maximum bioluminescence of

Maximum bioluminescence in *Pyrocystis noctiluca* was measured in the fall of 1994 and 1995 while minimum bioluminescence was measured in the spring of 1994 and 1996 (Figures 7ad). Maximum levels of nitrates for both years were in the summer, a time of maximum upwelling in the Southern California Bight. Maximum levels of nitrates preceded maximum bioluminescence for both years (Figure 7c) to possibly explain these seasonal changes in a photosynthetic bioluminescent dinoflagellate. Nitrate levels (M L-1) were averaged seasonally and compared with bioluminescence (Figure 7b). Both trends exhibit similar amplitudes, i.e., lower levels of nitrates were present in summer and fall of 1994 when

*Protoperidinium pellucidum* at San Clemente Island.

Limited measurements were conducted on *P. curtipes* and *P. divergens*. These cells produced more bioluminescence in the spring '94 than the following summer while *P. depressum* cells in the summer '94 were brighter than the previous spring months (Table 9). *P. leonis* cells were observed to produce more bioluminescence in spring '94 than in spring '95.


Table 9. Significant differences of light output seasonally in *Protoperidinium* species from 1994 - 1995.

### **3.4.3** *Ceratium fusus*

Significant seasonal differences of light output were observed from 1994-1996 in small and larger cells of *C. fusus*. Fall '94 cells produced more bioluminescence than winter '95 cells and winter '96 cells. In contrast, winter '96 cells produced more bioluminescence than fall '95 cells (Table 10). Between years, fall '94 cells were brighter than fall '95 cells while winter '96 cells exhibited more bioluminescence than winter '95 cells. Light output in larger cells of *C. fusus* showed that spring '96 were brighter than in fall '95 and winter '96. Larger cells of *C. fusus* were significantly brighter than smaller *C. fusus* cells for fall '95, winter '96 and spring '96.


n.s. = not significant

Table 10. Significant differences of light output seasonally in *Ceratium fusus* from 1994 – 1996.

Limited measurements were conducted on *P. curtipes* and *P. divergens*. These cells produced more bioluminescence in the spring '94 than the following summer while *P. depressum* cells in the summer '94 were brighter than the previous spring months (Table 9). *P. leonis* cells

were observed to produce more bioluminescence in spring '94 than in spring '95.

*P. curtipes* **Spr'94 - Sum'94 Spr > Sum p < 0.2** 

*P. depressum* Sum'94 - Spr'94 Sum > Spr p < 0.1

*P. divergens* Spr'94 - Sum'94 Spr > Sum p < 0.2

*P. leonis* Spr'94 - Spr'95 Spr'94 > Spr'95 p < 0.05

1994 - 1995.

spring '96.

n.s. = not significant

**3.4.3** *Ceratium fusus*

Table 9. Significant differences of light output seasonally in *Protoperidinium* species from

Significant seasonal differences of light output were observed from 1994-1996 in small and larger cells of *C. fusus*. Fall '94 cells produced more bioluminescence than winter '95 cells and winter '96 cells. In contrast, winter '96 cells produced more bioluminescence than fall '95 cells (Table 10). Between years, fall '94 cells were brighter than fall '95 cells while winter '96 cells exhibited more bioluminescence than winter '95 cells. Light output in larger cells of *C. fusus* showed that spring '96 were brighter than in fall '95 and winter '96. Larger cells of *C. fusus* were significantly brighter than smaller *C. fusus* cells for fall '95, winter '96 and

**SMALL CELLS** 

**LARGE CELLS**

**Difference in light output between** 

Table 10. Significant differences of light output seasonally in *Ceratium fusus* from 1994 – 1996.

**Fall'94 - Win'95 Fall > Win p < 0.02 Fall'94 - Win'96** Fall > Win **p < 0.05 Fall'94 - Spr'96** p < 0.5 **n.s. Win'96 - Fall'95** Win > Fall **p < 0.2 Seasons between years Fall'94 - Fall'95** Fall'94 > Fall'95 **p < 0.01 Win'96 - Win'95** Win'96 > Win'95 **p < 0.1** 

**Spr'96 - Win'96** Spr > Win **p < 0.05 Spr'96 - Fall'95** Spr > Fall **p < 0.2 Fall'95 - Win'96** p < 0.5 **n.s.** 

**large and small cells Fall'95** Large cells > small cells **p < 0.001 Win'96** Large cells > small cells **p < 0.01 Spr'96** Large cells > small cells **p < 0.05** 

#### **3.4.4 Seasonal trends of dinoflagellate bioluminescence, nitrates, and Chl** *a*

Maximum bioluminescence in *Protoperidinium pellucidum, Pyrocystis noctiluca, Ceratium fusus*, and *Gonyaulax polyedra* was observed in either fall or winter for 1994–1996. Maximum bioluminescence cell-1 in *P. pellucidum* occurred in winter 1995 and during the following fall. Bioluminescence in this species was lower in summer '94 and again in summer '95 (Figures 6a,b). The percent of peak bioluminescence (the peak refers to maximum bioluminescence measured in winter '95 and fall '95) varies with season with values as low as 30% for summer '94 and 20% for summer '95 (Figure 6b). Because *Protoperidinium* dinoflagellates are nutritionally dependent on other algal species, any change of algal biomass in waters adjacent to SCI might impact the growth, maintenance and luminescent potential of *Protoperidinium*. Extracted Chl *a* showed a similar periodicity as did mean bioluminescence cell-1 in *P. pellucidum* from summer '94 through summer '95. Maximum Chl *a* and mean bioluminescence cell-1 levels increased in winter 1995 and in spring 1995 (Figure 7a). The seasonal mean bioluminescence cell-1 and the seasonal mean Chl *a* in the waters off SCI were positively correlated (Figure 6c). Bioluminescence in *P. pellucidum* was not significantly different between winter and spring quarter 1995, but was significantly brighter than the preceding summer and fall quarters and the ensuing summer 1995 quarter (Table 6).

Fig. 6. (b) 1994 to 1996 year comparison of percent of maximum bioluminescence of *Protoperidinium pellucidum* at San Clemente Island.

Maximum bioluminescence in *Pyrocystis noctiluca* was measured in the fall of 1994 and 1995 while minimum bioluminescence was measured in the spring of 1994 and 1996 (Figures 7ad). Maximum levels of nitrates for both years were in the summer, a time of maximum upwelling in the Southern California Bight. Maximum levels of nitrates preceded maximum bioluminescence for both years (Figure 7c) to possibly explain these seasonal changes in a photosynthetic bioluminescent dinoflagellate. Nitrate levels (M L-1) were averaged seasonally and compared with bioluminescence (Figure 7b). Both trends exhibit similar amplitudes, i.e., lower levels of nitrates were present in summer and fall of 1994 when

Seasonal Changes of Bioluminescence in

both trends for both years.

*noctiluca* at San Clemente Island.

Photosynthetic and Heterotrophic Dinoflagellates at San Clemente Island 41

Fig. 7. (b) Seasonal differences in mean bioluminescence of *Pyrocystis noctiluca* and mean nitrates in waters surrounding San Clemente Island from 1994-1996. (c) Correlation of seasonal means of *Pyrocystis noctiluca* bioluminescence and mean nitrates. Mean nitrates were shifted to the right by 1 season to illustrate temporal and magnitude similarities in

Fig. 7. (d) 1994 to 1996 comparison of percent of maximum bioluminescence of *Pyrocystis* 

compared to summer and fall nitrate levels in1995. Bioluminescence showed similar trends for the same period (r= 0.859; p < 0.02). Less bioluminescence was measured in cells collected in fall '94 than in cells measured in fall '95. Spring bioluminescence was less than fall bioluminescence in *P. noctiluca* for both years (Figure 8d). Spring '94 bioluminescence was approximately 40% of the maximum of fall '94 and approximately 65% of maximum for fall '95.

Fig. 6. (c) Correlation of seasonal mean bioluminescence in *Protoperidinium pellucidum* with seasonal mean Chl *a* at san Clemente Island from summer 1994 through sumer 1995.

Fig. 7. (a) Seasonal differences in *Pyrocystis noctiluca* bioluminescence at San Clemente Island from 1994-1996. Error bars represent 1 standard deviation of the seasonal means.

compared to summer and fall nitrate levels in1995. Bioluminescence showed similar trends for the same period (r= 0.859; p < 0.02). Less bioluminescence was measured in cells collected in fall '94 than in cells measured in fall '95. Spring bioluminescence was less than fall bioluminescence in *P. noctiluca* for both years (Figure 8d). Spring '94 bioluminescence was approximately 40% of the maximum of fall '94 and approximately 65% of maximum for

Fig. 6. (c) Correlation of seasonal mean bioluminescence in *Protoperidinium pellucidum* with seasonal mean Chl *a* at san Clemente Island from summer 1994 through sumer 1995.

Fig. 7. (a) Seasonal differences in *Pyrocystis noctiluca* bioluminescence at San Clemente Island

from 1994-1996. Error bars represent 1 standard deviation of the seasonal means.

fall '95.

Fig. 7. (b) Seasonal differences in mean bioluminescence of *Pyrocystis noctiluca* and mean nitrates in waters surrounding San Clemente Island from 1994-1996. (c) Correlation of seasonal means of *Pyrocystis noctiluca* bioluminescence and mean nitrates. Mean nitrates were shifted to the right by 1 season to illustrate temporal and magnitude similarities in both trends for both years.

Fig. 7. (d) 1994 to 1996 comparison of percent of maximum bioluminescence of *Pyrocystis noctiluca* at San Clemente Island.

Seasonal Changes of Bioluminescence in

(Figure 7a).

Photosynthetic and Heterotrophic Dinoflagellates at San Clemente Island 43

which might be explained by the availability in the diet of diatoms and *Gonyaulax polyedra*

 Increased levels of Chl *a* were measured in the winter and spring '95 and were strongly correlated with increased *P. pellucidum* bioluminescence. Species of *Protoperidinium* are known to graze on *G. polyedra* in laboratory studies (Buskey et al., 1992; Latz and Jeong 1993; Jeong and Latz 1994). Latz (1993) demonstrated the maintenance of *Protoperidinium divergens* growth, survival, and bioluminescence capacity when grazing on a variety of dinoflagellates, but found maximum bioluminescence when the diet was solely *G. polyedra*. The winter '95 period within the Southern California Bight was characterized by an extensive red tide and extended from Santa Barbara south to San Diego and west to San Clemente Island*. G. polyedra* was the principal dinoflagellate present, reaching concentrations of approximately 16,000 cells l-1 in January 1995, although increases in *Protoperidinium* spp. were also observed (Lapota et al., 1997). Heavy rainfall was recorded during this winter period (17-18 inches, as compared with the norm of 5-10 inches) and consequently extensive runoff was observed along the entire southern California coast. Total bioluminescence (photons ml-1 year-1) was positively correlated with rainfall (inches year-1) for a 4 year period in San Diego Bay (1992-1996) (Lapota et al., 1997). Nitrates and trace metals are carried off from land with the runoff into surface waters (Dugdale and Goering 1967). Thus, the *G. polyedra* red tide was probably triggered by extensive runoff including nutrients such as nitrates from this "wet" year which in turn stimulated growth of phytoplankton grazed by *Protoperidinium pellucidum* and other *Protoperidinium* species. Increases in bioluminescence were observed in more than 60% of all rain events from 1992- 1996 in San Diego Bay (Lapota et al., 1997). Others have observed these sudden blooms and they often occur in spring or summer following heavy rains that produce nutrient-rich land runoff (Eppley, 1986). The reason for a fall '95 peak in *P. pellucidum* bioluminescence is unknown but may be due to grazing by *P. pellucidum* on lower numbers of *G. polyedra* and other algal cells. Upwelling and nitrate levels (Figure 8b) were greatest during the summer months and could result in a later increase in photosynthetic biomass in the fall. However, Chl *a* levels were actually low during the period when bioluminescence was high and may indicate previous grazing by *P. pellucidum.* Seasonal mean Chl *a* and mean bioluminescence cell-1 were strongly correlated (r = 0.962; p < 0.02) for 1994-1995 which may suggest that as Chl *a* levels increased, so did bioluminescence cell-1 (Figure 7c). These field measurements

support previous laboratory studies (Buskey et al., 1992; Latz and Jeong 1993).

 Both nitrates and mean bioluminescence cell-1 in *Pyrocystis noctiluca* show similar trends temporally and in magnitude (Figures 7b, 7c). Peak levels of nitrates were found in the summer months followed by increases in bioluminescence during the fall months. Nitrate levels were greater in summer '95 than in summer '94. Peak bioluminescence was also greater in fall '95 than in fall '94. Lagging data comparisons + 1 season for nitrates produced a strong correlation with bioluminescence for the entire 2 year period (r = 0.859; p < 0.02). That is, lower nitrate levels measured in 1994 correlated with lower bioluminescence in 1994 while greater nitrate levels correlated with an increased bioluminescence (Figure 7c). Peak bioluminescence was also observed to occur in the fall for both years (Figure 7d). The effect of nitrate on bioluminescent capacity within photosynthetic dinoflagellates is unclear, but perhaps may be related to the overall health of the cell and how *Pyrocystis, Gonyaulax* spp. and *Ceratium* partition their metabolic resources when nitrate satiated. Others have

Seasonal and yearly differences of bioluminescence in *Gonyaulax polyedra* and *Ceratium fusus* were also observed (Table 8, 10). While both data sets are incomplete with respect to a continuous record, the data do show a maximum bioluminescence in fall '94 for *C. fusus* and differences in bioluminescence in *G. polyedra* between winter '95 and winter '96.
